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Alps

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ALPS, the collective name for one of the great mountain sys tems of Europe stretching from the Gulf of Genoa to Vienna, and rising between the plains of northern Italy and of southern Ger many. The Alps do not present so continuous a barrier as the Himalayas, the Andes or even the Pyrenees. They are less exten sive than the Urals or the Scandinavian highlands. They are formed of numerous ranges, divided by comparatively deep val leys. This mountain mass forms a broad band, convex towards the north, while most of the valleys lie between the directions west to east and south-west to north-east. Many deep transverse valleys intersect the prevailing direction of the ridges and facil itate the passage of man, animals and plants, as well as of cur rents of air which mitigate the contrast that would otherwise be found between the climates of the opposite slopes. The derivation of the name Alps is uncertain; in all parts of the great chain itself the term Alp (or Alm in the Eastern Alps) is strictly ap plied to the high mountain pastures (see ALP), and not to the peaks and ridges of the chain.

Limits of the Alps.

Ifwe merely desire to distinguish the Alps from minor ranges the best limits are on the west (strictly speaking, south) , the Col d'Altare or di Cadibona (I ,6 24f t.) , lead ing from Turin to Savona and Genoa, and on the east the line of the railway over the Semmering Pass (3, 215 f t.) from Vienna to Marburg in the Mur valley, and on by Laibach to Trieste. An Italian commission in 1926 placed the limit on the east at a line from Vienna through Graz to Fiume. But if we confine the term to those parts where the height is sufficient to support perpetual snow, the limit to the west will be the Col di Tenda (6,145ft.), leading from Cuneo (Cori) to Ventimiglia, while on the east our line will be the route over the Radstadter Tauern (5,7o2ft.) and the Katschberg (5.384f t.) from Salzburg to Villach in Carinthia, and thence by Klagenfurt to Marburg and so past Laibach in Carniola on to Trieste.

On the north side, the Alps (in either sense) are definitely bounded by the Rhine from Basle to the Lake of Con stance, the plain of Bavaria and the low foot-hills from Salzburg to the neighbourhood of Vienna. The waters of the northern slope of the Alps find their way either into the North sea through the Rhine, or ir:.to the Black sea by means of the Danube, not a drop reaching the Baltic sea. On the south side the mountains from near Turin to near Trieste subside into the great plain of Pied mont, Lombardy and Venetia. The true west section of the Alps runs, from near Turin to the Col di Tenda, in a southerly direc tion, then bends east to the Col d'Altare, which divides it from the Apennines.

Divisions.—TheAlps consist of a main chain, with ramifica tions, and of several minor chains. They form a single connected whole as contrasted with the plains at their base, the only breaks in them being mountain passes at high altitudes. For the sake of convenience the best marked passes have long been used to serve as limits within the chain, whether to distinguish several great divi sions or to break up these into smaller ones. W. A. B. Coolidge's system considers only its topographical aspect. The divisions given lie between the Col di Tenda and the route over the Rad stadter Tauern. Three main divisions are generally distinguished: the Western Alps, extending from the Col di Tenda to the Simplon Pass; the Central Alps from the Simplon Pass to the Reschen Scheideck Pass, and the Eastern Alps from the latter to the Rad stadter Tauern route, with a bend outwards towards the south east in order to include the higher summits of the South-Eastern Alps. Assuming these divisions, it is found convenient to sub divide the whole mountain system into 18 smaller groups-5 in the Western Alps, 7 in the Central Alps and 6 in the Eastern Alps. These, with the limits of each subdivision, are as follow:— Western Alps.—The Maritime Alps (from the Col di Tenda to the Col de 1'Argentiere). The Cottian Alps (from the Col de 1'Argentiere to the Mont Cenis Pass and west to the Col du Galibier) . The Dauphine Alps (from the Col du Galibier, west wards and southwards). The Graian Alps (from the Mont Cenis to the Little St. Bernard Pass). These are usually divided into three groups, the Central (the watershed between the two passes named), the Western or French, and the Eastern or Italian. The Pennine Alps (from the Little St. Bernard to the Simplon Pass).

Central Alps.—The Bernese Alps (from Lake Geneva to the Furka Pass, the Reuss valley and Lake Lucerne). The Lepontine Alps (from the Simplon to the Splugen and south to the Furka and the Oberalp Passes). The eastern portion of this range is sometimes named the Adula Alps (from the St. Gotthard to the Splugen Pass). The Todi Range (from the Oberalp to the Klau sen Pass). The Glarus Alps (north of the Klausen Pass). The Bernina Alps (from the Maloja to the Reschen Scheideck and the Stelvio, south and east of the Val Bregalia and of the Engadine and north of the Valtellina). The Albula Range (from the Splugen to the Fluela Pass, north and west of the Val Bregalia and of the Engadine). The Silvretta and Rhatikon Ranges (from the Fluela to the Reschen Scheideck and the Arlberg Pass).

Eastern Alps.—The Alps of Bavaria. Vorarlberg and Salz burg (north of the Arlberg Pass, Innsbruck, the Pinzgau and the Enns valley). The Central Tirol Alps (from the Brenner to the Radstadter Tauern Pass, north of the Drave valley and south of the Pinzgau and the Enns valley). This includes the Zillerthal and the Tauern ranges. The Ortler, Stubai and Oetzthal ranges (from the Reschen Scheideck and the Stelvio to the Brenner Pass, south of the Inn valley, and north of the Tonale Pass). The Lom bard Alps (from Lake Como to the Adige valley, south of the Valtellina and the Aprica and the Tonale Passes). This division includes the Adamello, Presanella, Brenta and Bergamasque ranges. The Dolomites of south Tirol (from the Brenner to the Monte Croce Pass, and south of the Pusterthal). The South Eastern Alps (east of the Monte Croce Pass). This division in cludes the Julian, Carnic and the Karawanken Alps.

In 1926 an Italian commission considered the subdivision of the Alps and their suggestions embodied several modifications of the above. (See Douglas W. Freshfield, Geog. Journ. Jan. 1928, p. 37.) Geology and Structure.—TheAlps form but a small portion of a great zone of crumpling which stretches in a series of curves from the Rif mountains of Morocco to beyond the Himalayas. The whole group of mountains may be conveniently called the Alpine-Himalayan group. Within this zone the crust of the earth has been ridged up into a complex series of creases and folds, out of which the great mountain chains of southern Europe and Asia have been carved by atmospheric and other agencies. Superficially, the continuity of the zone is broken at intervals by gaps of greater or less extent; these are due in part at least to the subsidence of portions of the folded belt and their subsequent burial by more recent accumulations. Such a gap is that between the Alps and the Carpathians.

This mountain system, which stretches a quarter of the way across the globe, is formed not of a single fold of the crust but of a number of such, often parallel to one another and to the general direction (trend) of the chain. The mountains of southern Europe are an exception to the last statement, for we find that five great mountain systems radiate from the Alps themselves. One arm stretches east through the Carpathians and another to the south east through the Dinaric Alps. The latter passes through Candia and Rhodes into the Taurus mountains, where it is joined by the continuation of the Carpathian branch, and east into the Iran Plateau and the Himalayas. This arm appears to cross southern China whilst there is a loop to the south forming the Burmese Malayan arc. The third arm stretches west from the mountains of Provence into the Pyrenees and the northern Spanish high lands; a fourth through Liguria, Corsica, Elba, the Apennines, Sicily, the Balearic Islands, the Baetic Cordillera, across the Strait of Gibraltar and into the Rif mountains of Morocco. This latter demarcation of the fourth arm is according to Staub, but Kober considers the Baetic Cordillera as part of the Provence Pyrenees branch, and thinks that the Apennines branch continues by way of Sicily directly into the Rif mountains. A fifth narrow chain stretches from Grenoble into the Jura moun tains. These several chains, forming one great mountain system, were uplifted during the same period of earth-movement and by the same set of causes. Each branch is in a certain sense a sepa rate unit but each is represented in the Alps which is the narrowest portion of the whole mountain belt, and in consequence every aspect of the geology of the Alps is of paramount importance when the whole chain is considered.

Sedimentary rocks form a large part of the Alps. These range from the Trias to the Miocene, but older rocks (Permian, Carbon iferous, Devonian, Silurian and possibly Cambrian) also occur and are of considerable importance, especially in the Eastern Alps. Crystalline gneisses and schists and igneous rocks also occur. There are many rock types of local importance which need special mention. Here we find the characteristic Tertiary rocks, Molasse, Nagelfluh and Flysch. The former consists of a remark ably uniform series which crops out along the northern border of the Alps in the Great Swiss plateau. To the south of this is the Flysch zone which attains more important dimensions in the east than in the west. Other types which have commanded uni versal interest are the Gosau beds, Verrucano and Schistes Lustres. An intensive study of the geology and structure of the Alps has been carried out during the last decade.

The Alps stand upon the site of a geosyncline which, from late Carboniferous times, through the whole of the Mesozoic period until the Miocene period, existed between the Eurasian (Foreland) landmass to the north and the African (Hinterland) landmass to the south. The sea which occupied this depression has been called by Suess and others the "Tethys." Great thicknesses of deposits were laid down in it, causing the floor to sink and thus enabling the sediments to be deposited at approximately the same depth below the sea level. Termier compared this geosyncline to a huge vice, the jaws of which moved slowly inwards concurrently as deposition was taking place between them. The Hinterland moved north ward toward the Foreland. Argand has suggested that, by this movement two geanticlines (arches) arose within the geosyncline, thus bringing about the following subdivision :—the Valais Geo syncline (north), the Brianconnais Geanticline, the Piedmont Geosyncline, the Dolin Geanticline and the Canavese Geosyncline. The two geanticlines continued to increase in size as compression proceeded during the whole of the Mesozoic period until the cul mination of the movement in the Miocene. The compression was so great that the geanticlines rose completely out of the Tethys and were driven northward on to the Foreland in the form of huge recumbent folds, to which the name of "Nappes" is given. The geanticlines can now be identified in the Pennine Alps as the Great St. Bernard Nappe and the Dent Blanche Nappe. Further, the rise of these two structures also brought about the formation of other structures within the Alpine geosynclines; the Great St. Bernard Nappe forcing upward and forward the three Simplon Nappes which lie be Beath it, and the Dent Blanche Nappe simi larly bringing into being the Monte Rosa Nappe. There are thus in the Pennine Alps six major tectonic elements which arose from the Alpine geosyncline.

Apart from these, the Foreland and the Hinterland both played important roles and large tracts of the mountains belong to these divisions. Sedimentary rocks were laid down in epicontinental seas upon the peneplained Hercynian surfaces of these continental masses and these rocks, as well as the fundamental crystalline rocks, were affected by the Alpine earth-movements. The north ward movement of the Hinterland was so great that portions of it were driven completely over the geosynclinal rocks on to the Foreland itself. Sedimentary rocks of the same age belong to the Foreland, the Hinterland and the Geosyncline, but there are dis tinct differences in facies between them as well as differences within each group. Recumbent folding and overthrusting are com mon throughout the whole of the Alps, but the particular type of structure found in any locality depends upon the nature of the rocks and their location in one or other of the main divisions.

From a geological point of view it is convenient to divide the Alps into Western Alps and Eastern Alps along the Rhine-line (a north-south line through the Lake of Constance, Coire and the Septimer Pass) . The following is a summary of the chief tectonic divisions : Western Alps.—(a)The Jura mountains; (b) the great Swiss plateau of Tertiary rocks; (c) the Prealps, with exotic Palaeozoic, Mesozoic and Tertiary rocks; (d) the zone of the high Calcareous Alps of Switzerland (the Helvetide zone of Staub) ; (e) the "zone of Mont Blanc" in which are the crystalline Hercynian massifs, Mercantour, Pelvoux and Belledonne, Mont Blanc and Aiguilles Rouges, Gotthard, Aar and Gastern-Erstfeld (the Autochthonous massifs of Heim) ; (f) the Pennine zone, in which occur the Pen nine Nappes (Pennides of Staub) ; (g) the zone of the "Inner Roots," containing the "roots" of the Pennine, Austride and Dina ride Nappes.

Eastern Alps.

(a)The great Swiss plateau with Tertiary rocks; (b) the northern Flysch zone (the East Alpine equivalent of the zone of the high Calcareous Alps) ; (c) the zone of the Eastern Alps; (I) the northern Limestone zone of Triassic, Juras sic and Cretaceous rocks; (2) the Greywacke zone of schists and limestones of Palaeozoic age ; (3) the central zone, forming the chief mountain tracts of the Eastern Alps and built up chiefly of Austride Nappes; (4) the Pennine "windows" which occur within the central zone and in which Pennine Nappes are found ; (d) the Dinaride zone in which the Dinaride Nappes occur and which is formed of Palaeozoic and Mesozoic rocks and several plutonic intrusions.

Of these divisions the Jura mountains, the great Swiss plateau, the zone of the high Calcareous Alps, the northern Flysch zone and the "zone of Mont Blanc" belong to the Foreland; the Pen nine zone, the Pennine "windows" and part of the zone of the "Inner Roots" belong to the Alpine geosyncline, whilst the north ern Limestone zone, the Greywacke zone, the central zone, the Prealps, part of the zone of the "Inner Roots" and the Dinaride zone belong to the Hinterland.

Although the Foreland acted as a single unit during the Alpine earth-movements it did not possess a simple homogeneous struc ture. Some portions of it (e.g., the cen tral plateau of France, the Vosges, the Black Forest, the Bohemian mountains and the massifs of the "zone of Mont Blanc") resisted the northward advance of the folds, and the effect of this is well seen in the trend of the chain. To assist in forming a clear idea of this, a simple illustration will suffice.

Upon a table covered by a thick cloth lay two books (A and B) in the positions shown in the figure. If the two hands are placed flat upon the table and the cloth pushed in the direction indicated, it will at once be rucked up into a fold which will follow a curve not unlike that of the Alps. The precise form and ter of the folds will depend upon the ture of the cloth, position and number of obstructions, and other accidental circumstances. Moreover, if sufficient pressure be erted, the folds will lie one above the other as in the Alps selves. Here also there were two sets of obstructions, an outer group comprising the Maures-Esterel massif, central plateau of France, Vosges-Black Forest and Bohemian massifs ; and an inner group, the "zone of Mont Blanc." The outer group, well within the Foreland, determined the trend of the chains of the Basses and Dauphine Alps, the Jura mountains and Swabian Alps. The effect of the "zone of Mont Blanc," nearer the southern edge of the Foreland, is seen in the Pennine and Eastern Alps. Here Staub has identified ten distinct arcs, five in the Eastern Alps and five in the Western Alps. The latter are more distinct than those east of the Rhine-line, for the massifs of the "zone of Mont Blanc" all occur in the Western Alps, but the occurrence of arcs farther east indicates the presence of similar massifs buried beneath the Austrides. The presence of these is further indicated by the currence of culminations, which are portions of the true nappe mountains in which the lower elements have been forced to high altitudes, having been driven over elevated portions of the land. Denudation, especially river action, has brought about the removal of much of these upper structures and has revealed ent lower units in different districts. Vertical movement, during and since the orogenic period, has made this type of segmentation more marked. Between two culminations a tectonic depression occurs in which, owing to downward sagging, the uppermost tonic elements have been preserved from denudation. Staub has identified eleven culminations and eleven depressions in the Alps, and in the Western Alps the culminations occur in each case rectly behind the individual massifs of the "zone of Mont Blanc." The massifs of the "zone of Mont Blanc" are, generally ing, large granitic intrusions (batholiths), surrounded by line schists and gneisses with sedimentary rocks more or less highly metamorphosed. In the Aar, Mont Blanc and Pelvoux massifs "fan" structure has been identified, the granitic rocks being subdivided longitudinally by steep-sided synclines of crystalline schists. The larger massifs of the zone, viz., the Aar-Gotthard, Mont Blanc, Pelvoux and Mercantour, form an inner arc, whilst the smaller ones, viz., the Gastern-Erstfeld, Aiguilles Rouges and Belledonne, form an outer arc. Both arcs are open to the south and adjacent massifs are separated by zones of sedimentary rocks, many of which have been so highly metamorphosed as to be reduced to paragneisses. The Lotschental zone (paragneisses), the Chamonix sedimentary zone and the zone between the Pelvoux and the Belledonne occur between the two arcs. In the two former zones and in the adjacent massifs the "roots" of the nappes of the high Calcareous Alps are located. The sedimentary cover of the Aiguilles Rouges and the Gastern massifs has been called the Au tochthon. This term is also applied by some authorities to all that portion of the sedimentary cover of the Hercynian peneplained surface which has not suffered acute folding, such as is found in the zone of the high Calcareous Alps. Heim further calls the mas sifs of the "zone of Mont Blanc" the Autochthonous massifs. The Autochthon (in its wider sense) has not suffered acute folding such as is found in the other parts of the Alps, but the rocks are in contact with the surface upon which they were originally deposited.

In the high Calcareous Alps six nappes have been identified. These are called the Helvetides by Staub, but simply the nappes of the high Calcareous Alps by Collet and others. They are named as follows (from the highest to the lowest) :—(6)The Oberlaubhorn Nappe, (5) the Mont Bonvin Nappe, (4) the Plaine Morte Nappe, (3) the Wildhorn Nappe, (2) the Diablerets Nappe, (I) the Morcles Nappe.

The Morcles Nappe lies as a great recumbent fold upon the Autochthon, and has its "roots" in the zone of Chamonix. It is composed of sediments ranging from the Trias to the Eocene. Above it lies the Diablerets Nappe, the "roots" of which probably lie in the Mont Blanc massif. This nappe does not possess a reversed limb, this and much of the upper limb having been re placed by a "slide" (Bailey). The Wildhorn Nappe is the greatest of this group and is characterized by a number of digitations in the front of the structure, by disharmonic folding, and a large "involution." Its "roots" probably occur on the south side of the Mont Blanc massif. The three higher nappes (the Ultra-Helvetian Nappes of Heim) crop out in a belt 16m. long on the south side of the Wildhorn-Wildstrubel range, and again on the north side of the high Calcareous Alps in the "zone of Cols," where they form the Internal Prealps. In Eastern Switzerland (i.e., East of the Hasli-Tal) the following units occur :—The Santis-Drusberg Unit, the Axen Unit, the Glarner-Miirtschen Unit, the Parautochthon ous Nappes.

The upper unit (Santis-Drusberg) is an eastward extension of the Wildhorn Nappe, the Glarner-Miirtschen unit is homologous to the Diablerets Nappe, and the Parautochthonous Nappes rest upon the Autochthon and are homologous to the Morcles Nappe. The Axen unit is not represented in West Switzerland. Three nappes, digitations of one structure, are distinguished in the San tis-Drusberg unit, four in the Axen unit and two in the Glarner Miertschen unit.

With the exception of the Prealps, the great Swiss plateau bounds the high Calcareous Alps on the north. The plateau is underlain by Tertiary rocks, covered by glacial, fluvio-glacial and alluvial deposits. It forms a wide syncline between the Jura mountains and the Western Alps, and in it are gentle flexures, the most important of which is a central anticline which passes from Lake Constance to Lake Geneva. The sedimentary rocks of the Jura mountains are continuous with those of the Autochthon beneath the Tertiary rocks of the great Swiss plateau, but they do not show the same facies. They have been folded into anti clines and synclines, the trend of which is parallel to that of the Alps, but the folds are bunched together in the neighbourhood of the central plateau of France and the Vosges-Black Forest mas sifs. In the eastern part of the mountains the folding is compli cated by block faulting. This portion is known as the Jura table land whilst the remainder is called the Folded Juras. The folding has only a superficial character, for it dies out downward, the Anhydrite group (Middle Muschelkalk) not being folded. The beds of this latter horizon acted as a plane along which the folding took place, so producing a "decollement." A study of the tec tonics of the Jura mountains reveals a remarkable association between them and the Alps.

The Pennine Nappes (Pennides of Staub), being great recum bent folds which arose out of the Alpine geosyncline, consist of Palaeozoic rocks as crystalline cores, with envelopes of newer sedimentary rocks now highly metamorphosed and known as "schistes lustres." The evidence for the age of the schistes lus tres is sufficient to prove that they range from the Lower or Middle Trias to the Nummulitic Limestone (Eocene). They occur in the synclinal structures between the crystalline cores of the nappes and also along the frontal archbends of the latter. The three Simplon Nappes, Monte Leone (III.), Lebendun (II.), Antigorio (I.), crop out in the Ticino district, in the Lepontine culmination brought about by the obstacle of the Aar massif. (The figures I., II., etc., after the names of the nappes indicate the relative position of the structures, I. to VI. being Pennine Nappes and VII.–X. Austrides.) The nappes pass round the cul mination and are directly connected in the south with their roots. The schistes lustres associated with them are not so thick as else where in the Pennine Alps. The Great St. Bernard Nappe (IV.), which arose from the Brianconnais geanticline, occurs above the Simplon Nappes, the latter being regarded as major digitations of the higher structure. The Great St. Bernard Nappe is the most extensive of the Pennine units and stretches in an almost un broken outcrop from the Gulf of Genoa to the Simplon Pass. Schistes lustres mark the front of it and also separate it from the crystalline core of the Monte Rosa (V. ) Nappe, which forms the massifs of Monte Rosa, Grand Paradis, Ambin and Dora Maira and is in fact a major digitation of the highest Pennine Nappe. The Dent Blanche (VI.) Nappe, which arose from the Dolin geanticline, has suffered considerable denudation and its main out crop in the Dent Blanche-Weisshorn mountain mass is now isolated from the "roots." Here the nappe is in contact with the Great St. Bernard Nappe, for the Monte Rosa Nappe does not reach so far north and the Great St. Bernard has suffered backward folding.

The country east of the Rhine-line belongs principally to the Hinterland. In it we find several tectonic units, named the Aus trides by Staub, who also recognizes two divisions in the group, the Upper (Tirolides) and the Lower (Grisonides), both so named because of the location of their main outcrops. This is Staub's scheme, but Kober uses the name East Alpine Nappes for the Austrides and recognizes in them four main divisions. The Austrides overlie the Pennine Nappes in the Eastern Alps, for where denudation has been great the lower structures are exposed beneath the Austrides in what are known as "windows." In the Lower Engadine window, schistes lustres occur surrounded by Grisonide elements, whilst in the Hohe Tauern window there are tectonic elements correlated by Staub with the Monte Rosa and the Dent Blanche Nappes as well as schistes lustres. (Kober considers that the lowest elements here are homologous with the higher Simplon Nappes.) In the Semmering window, denudation has revealed the Grisonides beneath the Tirolides.

The Grisonides are divided into two major structures, the Campo (VIII.) Nappe and the Err-Bernina (VII.) Nappe, each of which has several digitations in its frontal portion. The lower of the two rests on the Margna (VI.) Nappe, which is homolo gous to the Dent Blanche Nappe. The Grisonides consist of crys talline cores surrounded by sedimentary rocks, the latter being peculiar in age and facies to each nappe. In the Rhatikon the Grisonides show "schuppen" structure (i.e., slices overthrust one upon another) and parts of them exhibit interesting sedimentary types, which are important in a study of the Prealps. The Tiro lides are similarly divided into two major structures, the Oetztal (X.) Nappe and the Silvretta (IX.) Nappe. The latter nappe is the greatest East Alpine structure and, being the lower of the two Tirolide elements, will occur to the north of the Oetztal Nappe in the "root" region, but the sedimentary cover of the latter has been driven over the Silvretta Nappe and forms the northern Limestone zone. The main outcrop of the Oetztal Nappe is in the Mur Alps of Styria, whilst the other forms the Silvretta mountain mass. The northern Limestone zone forms a wide belt from the Rhine-line to Vienna and has the structure of a great pile of overthrust masses of rocks ranging from the Trias to Cre taceous, the dolomite of the Trias being the principal member of the group. North of this zone is the northern Flysch zone, which is the eastern representative of the high Calcareous Alps.

Austride elements occur west of the Rhine-line, in the Prealps, which lie between the great Swiss plateau and the high Calcareous Alps and between the River Arve and the Lake Thun. The fol lowing tectonic elements have been identified in this region :- the External Prealps forming the northern portion and being over thrust upon the Molasse of the great Swiss plateau ; and the Inter nal Prealps on the southern margin. The Internal and External Prealps are probably connected and completely underlie the basin like structure filled by the higher elements of the Prealps. In these two zones the higher units of the high Calcareous Alps occur. Above the Internal Prealps is the Niesen Nappe (chiefly sand stones and conglomerates), which shows Pennine affinities; whilst above the External zone there are similar sandstones, etc., forming the zone of Gurnigel which is considered by some to represent the Niesen Nappe. The Median Prealps Nappe occurs above the zones mentioned and forms the greater part of the Prealps. Above it are the Simme Nappe and the Breche Nappe. These structures seem to show Austride affinities, and the association between them and the Austrides is further established by the occurrence of "Klippen" (i.e., frontal portions of nappes isolated by erosion) which have the character of a connecting link, resting upon the Mesozoic rocks of the high Calcareous Alps in the central Swiss region. Accord ing to Argand the "roots" of the Simme Nappe occur in the zone of Canavese, south of the Lepontine culmination. These also are west of the Rhine-line, but they are continuous with the "roots" of the other Austride elements farther east. In the zone of Cana vese the Dent Blanche Nappe is "rooted" together with the Aus trides, and in consequence of this Kober considers that this `nappe must belong to the East Alpine group (Austrides) and not to the Pennine chain.

The "roots" of the Pennine Nappes (the "inner roots") lie in a zone which stretches eastward from near Ivrea, through Locarno. The "roots" of the Austrides are in contact with these but on the south side of them. The nappes are vertical in this zone or even overturned toward the south. To the south again are the Dinaride Nappes. The boundary between the Austrides and the Dinarides (the Dinaric boundary) passes from the neighbourhood of the Italian Lakes to Meran, then east through the Drau Range to the south-east end of Bacher mountains, where it disappears beneath the Hungarian Plain. The tectonics of the Dinarides are compara tively simple. The term "nappes" is still used here by some authorities to designate the tectonic units; but the latter are very different from the nappes of other parts of the Alps, being essentially thrust masses. The extent of the thrusting is never very large. Moreover the units are not so strikingly different from one another in facies as is the case in other parts of the Alps. Kober recognizes four zones here, the Outer Zone (Adriatic), the Lower Dinaric Nappe, the Upper Dinaric Nappe and the High Dinaric Nappe. The stratigraphy of the Dinaric zone shows an important development of Up. Palaeozoic rocks, Silurian, De vonian, Carboniferous, Permian and Trias. Jurassic, Cretaceous and Flysch are also important in some units. This southern belt of the Alps is noted for its rich development of calcareous rocks. "Klippen" (outliers) of Dinaride elements occur resting upon the Oetztal Nappe in the Mur Alps district. The tectonics of the structures south of the Dinaric boundary show a southward direction of movement. This reverse direction of movement probably indicates one of the latest phases of the Alpine move ments. There has been considerable igneous activity in this region, but the intrusions are not all of the same age. The following are affected by Tertiary movements and must therefore belong to an earlier period:— the Kreuz, Iffinger, Brixen, and Riesenferner intrusions. The "Peri-Adriatic Intrusion Zone" (Salomon) con tains the following igneous bodies :—Ivrea, Baveno, Bergeller, Adamello, the tonalite of Eisenkappel and the granites of the Bacher mountains. These were not affected by Alpine movements and are, by many authorities, thought to be of slightly later date than those movements.

Main Chain.

Several important mountain groups are situ ated on one or other side of the watershed of the Alps and form almost independent ranges, connected with the main chain by a kind of isthmus : such are the Dauphine Alps, the Eastern and Western Graians, the entire Bernese Oberland, etc. The Alps, therefore, are not composed of a single range but of a great "divide," flanked on either side by other important ranges. Starting from the Col d'Altare or di Cadibona (west of Savona), the main chain extends first south-west, then north-west to the Col di Tenda, though nowhere rising much beyond the zone of conifer ous trees. Beyond the Col di Tenda the direction is first west then north-west to the Rocher des Trois Eveques (9,39oft.), just south of the Mont Enchastraye (9,695ft.), several peaks of about io,000ft. rising on the watershed, though the highest of all, the Punta dell'Argentera (10, 794f t.) stands a little way to its north. From the Rocher des Trois Eveques the watershed runs due north though of the two loftiest peaks of this region ; one, the Aiguille de Chambeyron (1 I, I 5 5 f t.) to the west and the other, the Monte Viso (12,6o9ft.) to the east of the watershed. From the head of the Val Pellice the main chain runs north-west and diminishes much in average height till it reaches the Mont Thabor (i 0,449f t. ), which forms the apex of a salient, which the main chain here pre sents towards the west. Hence the main watershed extends east, culminating in the Aiguille de Scolette (Ii,5ooft.) but makes a great curve to the north-west and back to the south-east before rising in the Rochemelon (ii,6o5ft.), a re-entering angle in the great rampart by which Italy is guarded. Thence the direction taken is north as far as the east summit (I 1,693f t.) of the Levanna, the watershed rising in a series of snowy peaks, though the loftiest point of the region, the Pointe de Charbonel (12,336 ft.), stands a little to the west. Once more the chain bends north west rising in several lofty peaks (the highest is the Aiguille de la Grande Sassiere (12,323ft.), before attaining the considerable de pression of the Little St. Bernard Pass (7,179ft.). Thence for a short way the direction is north to the Col de la Seigne (8,242ft.), and then north-east along the crest of the Mont Blanc chain, which culminates in the peak of Mont Blanc (15,782ft.), the loftiest in the Alps. A number of high peaks crown our watershed before it attains the Mont Dolent (12,543ft.). Thence after a short dip south-east, our chain takes near the Great St. Bernard Pass (8, I I 'ft.) the general easterly direction that it maintains through out the Pennine Alps till it reaches Monte Rosa, whence it bends north, making one small dip to the east as far as the Simplon Pass. In the Pennine Alps the main chain maintains a greaten average height than in any other part, but, though it rises in a number of lofty peaks, such as the Mont Velan (12,353ft.), the Matterhorn (14,782ft.), the Lyskamm (14,889ft.), the Nord End of Monte Rosa (15,13 2 f t.) and the Weissmies (13, 2 26f t.) , yet many of the highest points such as the Grand Combin (14,164ft.), the Dent Blanche (14,318f t. ), the Weisshorn (14,804f t. ), the true summit or Dufourspitz (15,2 17 f t.) of Monte Rosa itself, and the Dom rise on its northern slope and not on the main water shed. The chain between the Great St. Bernard and the Simplon sinks at barely half a dozen points below a level of io,000ft. East ward from the Simplon (6, 59 2 f t.) through the Lepontine Alps so far as the St. Gotthard (6,935ft.) the divide runs north-east, all the higher summits (including the Monte Leone, ri,684ft., and the Pizzo Rotondo, io,489ft.) rising on it, a curious contrast to the long stretch just described. From the St. Gotthard to the Maloja (5,96oft.) the watershed between the basins of the Rhine and Po runs east as a whole, though making two great dips towards the south first to near the Vogelberg (io,565ft.) and again to near the Pizzo Gallegione (I o, 20 i ft.), so that it presents a broken and irregular appearance. Its highest point is the Rheinwaldhorn (I I,149ft.).

From the Maloja Pass the main watershed dips south-east for a short distance, and then east and nearly over the highest summit of the Bernina group, the Piz Bernina (13,3o4ft.) to the Bernina Pass (7,645ft.) Thence to the Reschen Scheideck Pass (4,954ft.) the main chain is ill-defined, though on it rises the Corno di Campo (Io,844ft.), beyond which it runs slightly north-east, past the sources of the Adda and the Frael Pass (6,398ft.), sinks to form the depression of the Of en Pass (7, 5 23 f t.) , soon bends north and rises once more in the Piz Sesvenna (Io,568ft.). The break in the continuity of the Alpine chain marked by the deep valley, the ti'intschgau, of the upper Adige is one of the most remarkable features in the orography of the Alps. The chief source of the Adige is the little Reschen lake, which is only I 3 f t. below the Reschen Scheideck Pass (4,9o2ft.) and but 5m. from the Inn valley. East of this pass the main chain runs north-east to the Brenner Pass along the snowy crest of the Oetzthal and Stubai Alps, the loftiest point on it being the Weisskugel (12,291ft., Oetz thal), for the highest summits both of the Oetzthal and of the Stubai districts, the Wildspitze (12,382ft.) and the Zuckerhutl (II,52oft.), stand a little to the north.

The Brenner (4,495f t.) is almost the lowest of all the great motor road passes across the main chain, and has always been the chief means of road communication between Germany and Italy. For some way beyond it the watershed runs east over the Hoch feiler (11,559ft.) the highest crest of the Zillerthal Alps. A little farther, at the Dreiherrenspitze (Ii,5ooft.), we have to choose be tween following the watershed south, or keeping due east along the highest crest of the Greater Tauern Alps. (a) The latter course is adopted by many geographers. The watershed (though not the chief Alpine watershed) continues east through the Greater Tauern Alps, culminating in the Gross Venediger (12,008f t. ), for the Gross Glockner (12,461 ft.) rises to the south. Our chain bends north-east near the Radstadter Tauern Pass (5,7o2ft.) and preserves that direction through the Lesser Tauern Alps to the Semmering Pass (3,225ft.). (b) On the other hand, from the Drei herrenspitze the true main watershed of the Alpine chain dips south, passes over the Hochgall (11,287ft.), the culmination of the Rieserferner group, and then sinks to the Toblach Pass (3,967ft.) but a little east of the great Dolomite peak of the Drei Zinnen (9,837ft.) it bends east again and rises in the Monte Cogliano (9,128ft., the monarch of the Carnic Alps). Soon after our water shed makes a last bend to the south-east and culminates in the Terglou (9,400ft.), the highest point of the Julian Alps, though the Grintovc (8,429ft., the culmination of the Karawanken Alps) stands more to the east. Finally our watershed turns south and ends near the ,great limestone plateau of the Birnbaumerwald, be tween Laibach and Gorz.

Principal Passes.

TheAlps have never formed an impassable barrier. The spots at which they are crossed are called passes and are the points at which the great chain sinks to form depressions. Hence the oldest name for such passes is Mont (still retained in cases of the Mont Cenis and the Monte Moro) ; it was long before this term was especially applied to the peaks of the Alps, which, with a few rare exceptions (e.g., the Monte Viso was known to the Romans as Vesulus), were simply disregarded. The native inhabitants of the Alps were naturally the first to use the alpine passes, but to the outer world these passes first became known when the Romans traversed them in order to conquer the world beyond. For obvious reasons the Romans, having once found an easy pass did not trouble to seek for harder routes. The passes known to them were comparatively few : they are, in topo graphical order from west to east, the Col de l'Argentiere, the Mont Genevre, the two St. Bernards, the Spliigen, the Septimer, the Brenner, the Radstadter Tauern, the Solkscharte, the Plocken and the Pontebba (or Saifnitz). The Mont Genevre and the Bren ner were the most frequented, while it will be noticed that in the Central Alps only two passes (the Splugen and the Septimer) were certainly known to the Romans. The Simplon is first cer tainly mentioned in 1235, the St. Gotthard (without name) in i 236, the Lukmanier in 965, the San Bernardino in 941. Even the Mont Cenis (from the I sth to the 19th century the favourite pass for travellers) is first heard of in 756 only. In the i3th century many hitherto unknown passes came into prominence, even some of the easy glacier passes. In the Western and Central Alps there is but one ridge to cross, to which access is gained by a deep-cut valley, though often it would be shorter to cross a second pass in order to gain the plains, e.g., The Mont Genevre, that is most directly reached by the Col du Lautaret. In the Eastern Alps it is generally necessary to cross three distinct ridges between the north and south plains, the central ridge being the highest and most difficult. The passes which crossed a single ridge, and did not in volve too great a detour through a long valley of approach, became the most important and the most popular, e.g., the Mont Cenis, the Great St. Bernard, the St. Gotthard, the Septimer and the Brenner. As time went on the travellers who used the great alpine passes could not put up any longer with the bad old mule paths. A few passes (e.g., the Semmering, the Brenner, the Tenda and the Arlberg) can boast of carriage roads constructed before i 800, while those over the Umbrail and the Great St. Bernard were not completed till the early loth century. Many of the carriage roads across the great alpine passes were constructed in the i 9th century, largely owing to the impetus given by Napoleon. As late as 1905, the highest pass over the main chain that had a carriage road was the Great St. Bernard (8,i ft.). More recently railway lines have been carried over or through the chain—there being the Brenner and Pontebba lines, both over passes, and the Col di Tenda, Mont Cenis, Simplon, St. Gotthard, Lotschen, Arlberg, Albula and Pyhrn through tunnels. There are also schemes for piercing the Splugen and the Hohe Tauern, both on the main ridge. Since the advent of motor-cars several old road-passes have been improved and new ways made.

Glaciers.—Becausethe Alps were explored and studied earlier than the other mountain systems of the world, the type of glacia tion found there has received the name "Alpine Type." It is simi lar to that of parts of the Himalayas, Andes, Rockies and the mountains of New Zealand but is different from that of Spitz bergen, Greenland, Alaska and the Polar regions (see GLACIERS). The main characteristics of the Alpine type consist of an elevated "catchment area" from which valleys pass down to lower altitudes. The highest peaks do not necessarily form the centres from which the largest glaciers radiate, but these latter arise where the topog raphy of the mountain masses is that of numerous depressions and wide hollows separated by rounded snow-capped peaks, as Mont Blanc or by steep-sided frost-eaten peaks and ridges as the Aiguilles. Snow accumulates in these hollows and is compacted into ice which differs in appearance and internal structure from ice formed in the normal way by freezing. It is known as "neve" (Fr.) or "firn" (Ger.) . This ice is forced downward by the weight of the accumulated snow above, or falls down as avalanches into the valley below, forming the valley glaciers characteristic of the Alps. The boundary between the neve and the valley glacier (the firn-line) is marked by a change in the character of the surface of the ice. Above the firn-line precipitation is greater than melting and so snow covers the surface, but below it the reverse is the case and the ice is exposed. In summer the firn-line is quite dis tinct, but generally some hundreds of feet below the limit of perpetual snow.

It is estimated that there are 1,200 separate glaciers and neve fields in the Alps, but many are mere accumulations of snow in small hollows which really form part of larger basins. The largest glacier in the Alps is the Aletsch Glacier which is 16m. long and with its neve and catchment area covers an area of over 5osq. miles. The lowest point reached by glaciers varies considerably; it is as low as 3,2ooft. above sea-level at Grindelwald, but the height is more often quite i,000ft. higher than this. The line of perpetual snow lies between 8,000ft. and 9, 50o feet. Its exact position varies locally; regions which rise above these limits form centres for the radiation of valley glaciers. The largest of such centres are in the Mont Blanc group, the Bernese Oberland (from Blumlisalp to the Wetterhorn) and in the Pennine Alps (from the Grand Combin to the Mischabel). The main chain boasts of more glaciers and neve than the subsidiary chains. Nevertheless, the three longest glaciers of the Alps, the Greater Aletsch (i6m.) and the Unteraar and the Viescher (each iom.), are in the Bernese Oberland. The longest glaciers in the main chain are the Mer de Glace and the Gorner (each 91m.).

During the Pleistocene Ice Age the whole chain was more than once covered by an ice sheet above which perhaps the main peaks stood out. Penck infers four ice-maxima, Bayer thinks there were only two. One of the intervals, it is generally agreed, witnessed a return of warm temperate conditions. The final retreat of the Pleistocene Ice Sheet proceeded by stages, and it has been suggested there was a serious regrowth of glaciers in early centuries of the last millenium B.C. Each stage was marked by a continu ous retreat of the ice front to higher altitudes, no movement or perhaps even a temporary advance occurring in the intervals. During historical times the movement of the fronts has not been very marked. In 1918 a general forward movement was noticed in most Alpine glaciers, the previous great advance commencing in 1818 and finishing in 1822. The smaller glaciers will, of course, show movement more quickly than the larger. This is illustrated in the case of the Aletsch Glacier, which has maintained the same position of its front for many years. In 1823 this glacier suddenly dropped its level (for reasons not understood) causing the level of Lake Marjelen, which is formed by the glacier obstructing the mouth of a tributary stream, to fall.

Lakes and Water Power.

Thelakes of the Alps are of several types. (See LAKE.) Lakes of the barrier type are formed in various ways, principally by terminal and lateral moraines, in rarer cases by land slides, alluvial fans or a glacier. Lake Zurich shows interesting phases of damming by various moraines ; Lake Mattmark is formed by a lateral moraine; Lake Marjelen is a classic example of a glacier acting as a dam. Examples of lakes of tectonic origin are Lake Joux, in the Jura region, which occurs in a syncline, and Lake Fahlen near Santis. Lakes formed by the solution of calcareous rocks are of two types : the "polje" and the "doline" types. Frequently the depressions occupied by these lakes were the sites of former glaciers, as proved by the lining of glacial clay which the lakes now possess. Lakes of these types are quite frequent in the limestone areas and examples are Lakes Dauben, Mutten and Seewli (the latter also being In a corrie). Lakes in depressions in water-bearing strata occur on moraines or on fluvio glacial material. No rivers feed them and they have no visible effluents. Examples of the formation of two small lakes from a large one by a lacustrine delta are the lakes of Thun and Brienz and of Silser and Silvaplana.

In recent years the Alps have become a most important source of hydro-electric power for industry, railway transport and light ing, and the amount of coal used is diminishing. Nowhere, even in the limestone districts, is the amount of water so small as to war rant the exclusive use of coal or other fuels. As the water is derived from melting snow and ice, there is no fear of summer shortage, but a winter stoppage may occur. Most of the great lakes of the subalpine region are used as sources of supply, as also are many of the smaller ones ; in the latter cases the level of water is frequently raised by a dam. The water is drawn from the bottom of the lake in order to ensure a constant supply in winter. Reservoirs are also constructed in suitable places. The choice of site depends upon several factors, e.g., the impermeable nature of the rocks forming the basin, an adequate supply of water, a mini mum amount of deposition of sediment within the basin and the geographical position. Old lake basins have been, transformed into reservoirs, e.g., the Barbarine, and many deep gorges have been so utilized. Electric power and lighting are to be found in remote villages.

In the Alps are the sources of the great rivers of western Europe—the Po, Rhone, Rhine and Danube (the actual source of the latter is in the Black Forest, but its main tributaries rise in the Alps). These rivers drain the south, west, north and east slopes respectively, and the Danube also drains the north slope. There exists a very close connection between the direction of the river valleys in the Alps and the geological structure. Most of the val leys are either parallel to or at right angles to the trend of the chains. Examples of the former are the Isere, the Upper Rhone and the Upper Rhine, and of the latter the rivers of the Pennine Alps.

Climate.—It is well known that as we rise from the sea-level into the upper regions of the atmosphere the temperature de creases. Mountain chains cause the prevailing winds to rise to higher altitudes, thus frequently bringing about the precipitation of snow or rain principally upon the windward side. The vast mass of snow, converted into glaciers, maintains a gradation of very different climates within the narrow space that intervenes between the foot of the mountains and their upper ridges; it cools the breezes that are wafted to the plains on either side, but its most important function is to regulate the water-supply of the large region traversed by Alpine streams. Nearly all precipitation during six or seven months is in the form of snow, gradually re leased by melting in the course of the succeeding summer ; even in the hottest and driest seasons the reserves accumulated in the form of glaciers maintain the regular flow of the greater streams. Nor is this all; the lakes that fill several main-valleys on the south side are somewhat above the level of the Lombardy plain, and afford inexhaustible water for that system of irrigation to which it owes its proverbial fertility.

Six regions or zones, which are best distinguished by their char acteristic vegetation, are found in the Alps. They are (a) the olive region, (b) the vine region, (c) the mountain region or the region of deciduous trees, (d) the subalpine region or the region of coniferous trees, (e) the Alpine region, (f) the glacial region. Local conditions of exposure to the sun, protection from cold winds or the reverse, as well as height above sea-level, are of primary importance in determining the climate and the corre sponding vegetation.

(a) The great plain of Upper Italy is colder in winter than the 13ritish Isles. The olive and the characteristic shrubs of the North Mediterranean coasts do not thrive in the open, but olives ripen in sheltered places at the foot of the mountains and along the deeper valleys and the lake shores. The evergreen oak is wild about Lake Garda, and lemons are cultivated on a large scale, with partial pro tection in winter.

(b) The vine is far more tolerant of cold than the olive, but to produce tolerable wine it demands, at the season of ripening, not much less warmth than the olive, about 68° F average. These conditions are satisfied in the deeper valleys of the Alps, and up to a considerable height on slopes exposed to the sun. Winter snow-covering helps the plant to resist severe and prolonged frosts.

(c) So many varieties of grain are grown under various cli matic conditions that their limits of cultivation are less useful for determining zones than are those of the chief deciduous trees— oak, beech, ash and sycamore. These do not reach exactly to the same elevation, nor are they often found growing together; but their upper limit corresponds accurately enough to the change from a temperate to a colder climate. This limit lies about 4,000 f t. above sea-level on the north side of the Alps, but on the southern slopes it often rises to 5,000ft., sometimes even, to 5,500 feet. The interference of man has in many districts almost ex tirpated these trees. Their place has been occupied by the Scotch pine and spruce, which suffer less from goats, the worst enemies of trees. The mean annual temperature differs little from that of the British Islands; but snow usually lies for several months, till it gives place to a spring and summer considerably warmer than the average of British seasons.

(d) The Subalpine is the region which mainly determines the manner of life of the peasant population of the Alps. Of the space lying between the summits of the Alps and the low country on either side roughly one-quarter is available for cultivation of which about one-half may be vineyards and corn-fields, while the re mainder produces forage and grass. About another quarter is utterly barren, consisting of snow-fields, glaciers, bare rock, lakes and the beds of streams. There remains about one-half, which is divided between forest and pasture, and it is the produce of this half which mainly supports the relatively large population. For a quarter of the year the flocks and herds are fed on the upper pas tures; but the true limit of the wealth of a district is the number of animals that can be supported during the long winter, and while one part of the population is engaged in tending the beasts and in making cheese and butter, the remainder is busy cutting hay and storing up winter food for the cattle. The larger villages are mostly in the mountain region, but in many parts of the Alps the villages stand in the subalpine region at heights varying from 4,00of t. to 5,5oof t. above sea-level, more rarely extending to about 6,000 feet. Coniferous trees, where they have not been artificially kept down, form vast forests. They protect the valleys from destructive avalanches, and, retaining the superficial soil by their roots, they mitigate the destructive effects of heavy rains. On very steep slopes avalanches have frequently torn up the trees, leaving long avenues of varying width through the forests. In such places and in valleys where they have been rashly cut away, and the waters pour down the slopes unchecked, every tiny rivulet be comes a raging torrent, that carries away the soil and subsoil from the grassy slopes and devastates the floor of the valley, covering it with debris and gravel. The prevailing species are the common spruce, the silver fir, the larch and the Scotch pine. The Siberian fir is also found. In the northern Alps the pine forests rarely surpass the limit of 6,000ft. above the sea, but on the south side they commonly attain 7,000f t., while the larch, Siberian fir and mughus often extend above that elevation.

(e) Throughout the Teutonic region of the Alps the word Alp is used specifically for the upper pastures where cattle are fed in summer, but this region is held to include the whole space between the uppermost limit of trees and the first appearance of permanent snow. Here the characteristic vegetation of the Alps is developed in its full beauty and variety. Shrubs are not wanting. Three species of rhododendron give masses of red or pink flowers; the common juniper rises higher still, along with three species of bil berry; and several dwarf willows attain nearly to the utmost limit of vegetation, the so-called limit of perpetual snow.

(f) On the higher parts of lofty mountains more snow falls in each year than is melted on the spot. A portion of this is carried away by the wind before it is consolidated ; a larger portion accu mulates in hollows of the surface, and, gradually converted into glacier ice, descends slowly into the deeper valleys, to swell peren nial streams. As on a mountain the snow does not lie in beds of uniform thickness, and some parts are more exposed to the sun and warm winds than others, we commonly find beds of snow alternating with exposed slopes covered with brilliant vegetation; and to the observer near at hand there is no appearance in the least corresponding to the term limit of perpetual snow, though the case is otherwise when a high mountain-chain is viewed from a distance, for the level at which large snow-beds show themselves along its flanks is approximately horizontal, in so far as conditions are similar. On the opposite sides of the same chain, exposure to sun or to warm winds may cause a wide difference in the level of permanent snow ; but in some cases the increased fall of snow on the side exposed to moist winds may more than compensate increased influence of the sun's rays. Still, even with these reserva tions, the so-called line of perpetual snow is not fixed. In some parts of the Alps the limit may be set at about 8,000ft. above the sea, while in others it cannot be placed much below 9,500 feet. As very little or no snow can rest on rocks that lie at an angle exceeding 6o°, some steep masses of rock remain bare even near the summits of the highest peaks, but as almost every spot offering the least hold for vegetation is covered with snow, few flowering plants are seen above i i ,000 feet. It is, however, want of soil rather than climatic conditions that checks the upward extension of the alpine flora. Increased direct effect of solar radiation com pensates for the cold nights, and in the few spots where plants have been found in flower up to a height of i 2,000f t., nothing has indicated that the processes of vegetation were arrested by the severe cold which they must sometimes endure. The climate of the glacial region has often been compared to that of the polar regions, but they are widely different. Here, intense solar radiation by day, which gives the surface when dry a temperature approaching 8o° F, alternates with severe night frost. There, a sun which never sets sends feeble rays that maintain a low equable temperature rarely rising more than a few degrees above the freezing-point. Hence the upper region of the Alps sustains a far more varied and bril liant vegetation.

Flora.—The Alps owe the richness and beauty of their plant life partly to their position as the natural boundary between "Baltic" and "Mediterranean" floras, but chiefly to the presence on their heights of a third flora which has but little in common with either of the others. The stronghold of this last, the dis tinctively "Alpine" flora, is the region above the tree-limit. Its closest relationship is with the flora of the Pyrenees ; but an alpine flora is characteristic of all the lofty mountains of central Europe. According to J. Ball, 2,010 well marked species of flowering plants occur within the limits of the Alps. If now we confine our atten tion to the alpine and higher regions of the Alps and exclude from our list all those plants which are not less abundant in the low lands, we have left some 700 species. We must observe, as re gards the plants of the lower alpine region, that it is the actual presence of a forest vegetation, rather than the theoretical tree limit, which affects their vertical distribution; so that, e.g., they overflow into the extensive clearings made by man in the pri maeval mountain forests. Indeed, an analysis of the composition of the alpine flora as a whole leads to the conclusion that the chief bond of union between its members consists in the treeless char acter of their habitat.

We may broadly distinguish two main geographical elements in the alpine flora, namely, the northern element and the endemic element. This division (which is not, however, strictly exhaustive) directs special attention to what is undoubtedly the most striking feature of the flora, namely, that of its 693 species no less than 271 reappear in the extreme north. This relation of the arctic to the alpine flora is all the more remarkable in view of the very impor tant differences between the arctic and alpine climates. The fol lowing circumpolar species are common, and widely diffused throughout the whole of the Alps : Silene acaulis, Dryas octo petala, Saxifraga oppositifolia, S. aizoides, S. stellaris, Erigeron al pinus, Azalea procumbens, Myosotis alpestris, Polygonum vivi parum, Salix retusa, S. herbacea, Phleum alpinum, Juniperus nana. The proportion of northern forms, as regards both species and individuals, increases until, on islands of rock above the snow line, it is equal to the endemic element. Northern flowers of the snow-region include Silene acaulis, Eritrichium nanum, and Are naria ciliata. On the other hand, typical endemic species of this highest zone are Androsace helvetica, A. glacialis, Petrocallis py renaica, and Cherleria sedoides. All the plants just named are "cushion-plants." Their compact, moss-like growth and general structural peculiarities are analogous adaptations to the dry cold of their habitat. Among the northern plants of the alpine zone, in the narrower sense of the term (i.e., of the region between the tree-limit and the snow-line), there is a marked predominance of species that affect moist localities; and, conversely, the majority of alpine flowers of wet habitat are found also in the north. For example, in the genus Primula, a highly characteristic genus of the alpine flora, whose members are among the most striking orna ments of the rocks, the single northern species, P. farinosa, grows only in marshy meadows. On the whole, then, adaptation to cold and wet is the note of the northern element.

During the glacial period, in the ice-free belt, between the northern ice-sheet and the vastly extended glaciers of the Alps, the two floras found refuge and congenial conditions ; fossils confirm this view. With the return of a milder climate, the so-called northern forms of the present alpine flora were split in two, one portion following close on the northern ice in its gradual retreat to the Arctic, the other following the shrinking glaciers till the plants were able to establish (or re-establish) themselves on the slopes of the Alps. The same explanation covers the case of the similarity of the flora (not merely as regards the northern ele ment) on all the high mountains of central Europe. Beyond this, disagreement begins between the most eminent writers on the sub ject. While some (e.g., Sir J. D. Hooker, Heer) regard the Arctic, and some (e.g., Wettstein) the Alps, as the original home of the bulk of the "northern" element, others (e.g., Ball, Christ) locate this in the highlands of temperate Asia. For it is a remarkable fact that, of the 230 northern species which are most typical of the far north, 182 are found also in the Altai (taking this as a collective name for the mountains that form the southern boun dary of Siberia). In any case, however, the migration of these plants to the Alps must for the most part have taken place via the Arctic. The possibility of any extensive east to west migration having taken place direct from the Altai to the Alps seems ex cluded by the fact that so% of the arctico-altaic alpine plants are absent from the Caucasus. On the whole, a common origin in the north for at least the arctico-altaic group of alpine plants seems to be the most reasonable hypothesis. A score of species are common to Alps and Altai, but a larger number of arctic-alpine forms are absent from the Altai.

Side by side with the northern element we find a group of spe cies usually spoken of as the xerothermic or meridional element. These do not, however, form an "element," in the strict geographi cal sense in which this term is otherwise used here. They are those species which, on general phyto-geographical grounds, must be regarded as having originated under steppe-like conditions. Their affinities are chiefly, with the present Mediterranean flora—about 5o are of presumably Mediterranean origin—and a large propor tion of them are restricted to the southern slopes of the Alps. The following, however, among others, are distributed throughout the whole, or a great part, of the range :—Colchicum alpinurn, Crocus vernus, Orchis globosa, Petrocallis pyrenaica, Astragalus depressus, A. aristatus, Oxytropis Halleri, Eryngium alpinurn, Erica cornea, Linaria alpina, Globularia nudicaulis, G. cordi f olia, Leontopodium alpinum. The last named (the well-known "edelweiss") is at the present day characteristic of the Siberian steppes. The presence of these plants among the alpine flora is traceable to the steppe like conditions which prevailed in central Europe both during the warmer interglacial periods and (probably) for a time after the close of the ice-age. Subsequently, as the climate of the plains assumed a colder and more humid character, they retired before the invading forests to the high mountains. Here, in the intenser insolation which they enjoy, they seem to find a compensation for the drawbacks incidental to the altitude.

As regards the endemic element as a whole, the question as to the time and place of its origin is of a highly complicated and con troversial nature. The question, too, in the case of this element, is necessarily of genetic rather than purely geographical scope. It must suffice to say that the weight of scientific opinion inclines to the view that at least the majority of endemic species are of pre-glacial origin, and are either strictly indigenous or products of the neighbouring lowlands. About 4o% of the endemic element in the alpine flora are endemic also in the narrower sense, i.e., they are confined to the Alps. The following is a list of the most thor oughly characteristic alpine plants—all of them ipso facto mem bers of the endemic element—which are at once peculiar to the Alps (or practically so) and widely distributed within the limits of the chain. These are :—Festuca pulchella, Carex microstyla, Salix caesia, Rumex nivalis, Alpine aretioides, Aquilegia alpina, Thlaspi rotundi f olium, Saxi f raga seguieri, S. aphylla, Astragalus leontinus, Daphne striata, Eryngium alpinum, Bupleurum stel latum, Androsace helvetica, A. glacialis, Gentiana bavarica, Phy teuma humile, Campanula thyrsoidea, C. cenisia, Achillea atrata, Cirsium spinosissirnum, Crepis terglouensis.

Fauna.—Thefauna of the lower zones in the Alps is, on the northern side of the chain, practically identical with that of cen tral Europe, and on the southern side with that of the Mediterra nean basin. But in the higher regions it presents,many features of special interest. It seems, therefore, best to treat here principally of the animal inhabitants of the high Alps.

Though among mammalia—as also birds—there are but few forms peculiar to the Alps, many interesting animals have found in the high mountains at least, a temporary refuge from man. The European bison, the urus, the elk, the wolf and the wild swine have disappeared. But the lynx (Lynx lynx) lingers in remote parts, as also the brown bear (Ursus arctos) in the dense forests of the Lower Engadine. The fox (Vulpes vulpes), the stone marten (Martes foina) and the stoat or ermine (Putorius er rninea) range in summer above the tree-limit. The Ungulata are represented by a few chamois (Rupicapra tragus) and a rare bou quetin or steinbock (Capra ibex). The former—the sole repre sentative, in western Europe, of the antelopes—is found else where only in the Pyrenees, Carpathians, Caucasus and the moun tains of eastern Turkey; the latter survives only in the eastern Graian Alps. Of the Rodentia the most interesting and conspicu ous is the marmot (Arctornys marmota), which lives in colonies close to the snow-line. The snow-mouse (Arvicola nivalis) is con fined to the alpine and snow regions, and is abundant at these levels throughout the whole chain of the Alps. The mountain hare (Lepus variabilis) replaces the common hare (Lepus europaeus) in the higher regions; though absent from the intervening plains it again appears in the north of Europe and in Scotland. Among the Insectivora, the alpine shrew (Sorex alpinus) is restricted to the Alps. Of the Cheiroptera (bats) only Vesperugo rnaurus is characteristically alpine.

The birds of the Alps are proportionately very numerous. The lammergeyer (Gypaetus barbatus) , once common, is now extremely rare, but the golden eagle (Aquila chrysaetos) still holds its own. Some of the smaller birds of prey are not uncommon, but there is none that can be regarded as specially characteristic either of the Alps as a whole or of the alpine region. As characteristic birds of the snow-region may be mentioned the alpine chough (Pyrrho corax alpinus), which is frequently seen at the summits even of the loftiest mountains, the alpine swift (Apes melba), the wall creeper (Tichodroma muraria), snow-finch (Montifringilla ni valis) and ptarmigan (Lagopus mutus) ; the geographical distri bution of this last being similar to that of the mountain hare. The black redstart (Ruticilla titys), though common in the lower regions, is also met with in fair numbers almost up to the snow line. The raven (Corvus corax) is fairly common in the alpine and sub-alpine regions. On the highest pastures we find, further, the alpine accentor (Accentor collaris) and the alpine pipit (An thus spipoletta). The crag-martin (Cotyle rupestris) haunts lofty cliffs. On the upper verge of the pine forests, or in the scrubby vegetation just beyond, the following are not uncommon :—black woodpecker (Picas martins), ring-ousel (Turdus torquatus), Bonelli's warbler (Phylloscopus bonellii), crested tit (Parus cris tatus), citril finch (Citrinella alpina), siskin (Clirysomitris spinus), crossbill (Loxia curvirostra), nutcracker (Nucifraga caryocatactes), blackcock (Tetrao tetrix) and the alpine varieties of the marsh-tit (Parus talustris borealis) and tree-creeper (Cer thia familiaris costae) .

The remaining classes of Vertebrata are sparsely represented in the high Alps, and what species occur are mostly common to the plains as well. Among the remaining land vertebrates only the black salamander (Salamandra atra) is exclusively alpine. This animal, though a member of the Amphibia, is terrestrial and viviparous.

The former connection between the Arctic and the Alps, which has left such unmistakable traces in the present alpine flora, affords, as regards the fauna also, the only possible explanation of the present geographical distribution of many alpine forms; but it is chiefly among the Invertebrata that we find this 'collateral testimony to the influence of the glacial period. In this respect we may note that two small crustaceans, Diaptomus bacillifer and D. denticornis, swarm in the ice-cold waters of the highest alpine tarns throughout the entire chain ; and the former of these is also a characteristic inhabitant of pools formed from melting snow in the extreme north. Among the remaining divisions of Inverte brata special mention may be made of the air-breathing Arthro poda—on the whole the most important and interesting group. About one-third of the animals belonging thereto that occur in the higher regions are exclusively alpine (or alpine and northern) ; these characteristically alpine forms being furnished chiefly by the spiders, beetles and butterflies. Most numerous are the beetles. Those of the highest zone are remarkable for the great predom inance of predacious species and of wingless forms. In this last respect they present a striking analogy with the endemic coleop terous fauna of oceanic islands. As for the butterflies, not more than one-third of the species found in the alpine region occur in the neighbouring lowlands. The relations between alpine butter flies and plants are especially interesting, as regards not only their bionomic interdependence but also the analogies of their geo graphical distribution. It should be noted that butterflies are the chief agents in securing the continued existence of such alpine flowers as depend on insect fertilization, the other insect fertilizers being mostly wanting at great heights.

Inhabitants of the

Alps.—From ancient times we have only scanty mention of Alpine peoples by classical writers, with a few references to conquests by Augustus and to later movements of Teutonic tribes of the 5th and 6th centuries. To them, as to Frankish kings and emperors, the Alps offered a route rather than a residence. In the case of the Western Alps (minus the bit from the chain of Mont Blanc to the Simplon, which followed the for tunes of the Valais), a prolonged struggle for the Alpine region took place between the feudal lords of Savoy, the Dauphine and Provence. In 1349 the Dauphine fell to France, while in 1388 the county of Nice passed from Provence to the house of Savoy, which also held Piedmont as well as other lands on the Italian side of the Alps. The struggle henceforth was limited to France and the house of Savoy, but little by little France succeeded in pushing back the house of Savoy across the Alps, thus forcing it to become a purely Italian power. One turning-point in the rivalry was the treaty of Utrecht 0713), by which France gave up to Savoy the districts (all forming part of the Dauphine and lying on the Italian slope of the Alps) of Exilles, Bardonneche, Oulx, Fenestrelles and Château Dauphin, while Savoy handed over to France the valley of Barcelonnette, situated on the western slope of the Alps and forming part of the country of Nice. The final act in the long-continued struggle took place in 186o, when France obtained by cession the rest of the county of Nice and also Savoy, thus remaining sole mistress on the western slopes of the Alps.

In the Central Alps the chief event, on the north side of the chain, is the gradual formation from to 1815 of the Swiss Confederation and the independent confederations of the Grisons and the Valais, which became full members of the Swiss Confed eration only in 1803 and 1815 respectively. The Forest Cantons in the 15th century won the Val Leventina as well as Bellinzona and the Val Blenio (though the Ossola valley was held for a time only), while the Grisons added to the Val Bregaglia (which had been given to the bishops of Coire in 96o by the emperor Otto I.) the valleys of Mesocco and of Poschiavo. Further, in 1512, the Swiss Confederation won the valleys of Locarno with Lugano, which, combined with the 15th century conquests by the Forest Cantons were formed in 1803 into the new Canton of Ticino or Tessin. On the other hand, the Grisons won in 1512 the Val tellina, with Bormio and Chiavenna, but in 1797 these regions were finally lost to it as well as to the Swiss Confederation, though the Grisons retained the valleys of Mesocco, Bregaglia and Poschiavo, while in 1762' it had bought the upper bit of the valley of Munster that lies on the southern slopes of the Alps.

In the Eastern Alps the political history relates simply to the advance or retreat of the house of Habsburg. The Habsburgers' ruined castle still stands in the lower valley of the Aar; they lost this district to the Swiss in 1415, and won the duchy of Austria with Styria in 1282, Carinthia and Carniola in 1335, Tirol in 1363 and the Vorarlberg in bits from 1375 to 1523, not to speak of minor "rectifications" of frontiers on the northern slope of the Alps. But on the other slope their progress was slower, and finally less successful. It is true that they early won Primiero (1373), as well as (1517) the Ampezzo valley and several towns to the south of Trent. In 1797 they obtained Venetia proper, in 1803 the secularized bishoprics of Trent and Brixen (as well as that of Salzburg, more to the north) besides the Valtellina region, and in 1815 the Bergamasque valleys, while the Milanese had belonged to them since 1535. But in 1859 they lost to the house of Savoy both the Milanese and the Bergamasca, and in 1866 Venetia proper also, and in 1918-19 the Trentino. The gain of the Milanese in 1859 by the future king of Italy (1861) meant that Italy then won the valley of Livigno (between the Upper Engadine and Bormio), besides the county of Tenda (obtained in 1575, and not lost in 186o), with the heads of certain glens in the Maritime Alps, reserved in 186o for reasons connected with hunting. After a decisive plebiscite, Vorarlberg requested to be admitted into the Swiss Confederation in 1919, but the request was not granted in the Treaty of St. Germain. By this same treaty, a large portion of the Southern Alps, much of which was held by them at the close of the World War (1914-18), passed into the legal possession of Italy, and the boundary between that country and Austria was readjusted. The southern frontier of Austria was not altered along the Swiss section, but eastward from Gruben it now passes through Dreiherrn Spitz, then south-east of Helm Spitz and along the sum mit ridge of the Carnic Alps to Grintove, and northward to Unter Drauberg, where it again turns east, and on to Spielfeld. The frontier between Italy and Yugoslavia branches off and passes southward from Tarvis (south-west of Villach). By the addition of this territory of German-speaking peoples to Italy the number of sections of the Alps in which the natives do not speak the tongue of the country was increased. In Italy there are also some French-speaking districts (the Waldensian valleys as well as the Aosta and Oulx valleys) . In Switzerland there are Italian-speaking regions, as well as some spots (in the Grisons) where the old Romance dialect of Romansch or Ladin survives ; while in Aus tria, besides German, Italian and Ladin, we have a Slavonic-speak ing population in the South-Eastern Alps. The highest perma nently inhabited village in the Alps is Juf, 6,998ft. (Grisons); while in the French Alps, L'Ecot, 6,713ft. (Savoy), and St. Veran, 6,726ft. (Dauphine), are rivals; the Italian Alps boast of Trepalle, 6,788ft. (between Livigno and Bormio), and the Tiro lese Alps of Ober Gurgl, 6,3 2 2 f t., and Fend, 6, 2 I I f t. (both in the Oetzthal).

Exploration of the High Alps.

About 20 glacier passes were certainly known before i600, about 25 more before 170o and yet another score before 1800 ; but though the attempt of P. A. Arnod (an official of the duchy of Aosta) in 1689 to "re-open" the Col du Geant may be counted as made by a non-native, we do not come upon another case of the kind till the last quarter of the i8th century. The two earliest recorded ascents of high peaks were due to non-natives, that of the Rochemelon in 1358 having been under taken in fulfilment of a vow and that of the Mont Aiguille in 1492 by order of Charles VIII. of France, in order to destroy its repu tation for inaccessibility; in 1555 Conrad Gesner climbed the grassy mound of the Gnepfstein, the lowest and the most westerly crf the seven summits of Pilatus. The two first men who really sys tematically explored the regions of ice and snow were H. B. de Saussure (174o--99), as regards the Pennine Alps, and the Bene dictine monk of Disentis, Placidus a Spescha (1752-1833, most of whose ascents were made before 1806), in the valleys at the sources of the Rhine. In the early 19th century the Meyer family of Aarau conquered in person the Jungfrau (18 I i) and by deputy the Finsteraarhorn 0812), besides several glacier passes, their energy being entirely confined to the Bernese Oberland. Their pioneer work was continued, by a number of Swiss, among whom were Gottlieb Studer (1804-90) of Bern, and Edouard Desor (I 811-8 2) of Neuchatel. The first-known English climber in the Alps was Colonel Mark Beaufoy (1764-18 2 7) , who in 1787 made an ascent (the fourth) of Mont Blanc, a mountain to which his fellow-countrymen long exclusively devoted themselves, with a few noteworthy exceptions, such as Principal J. D. Forbes (18o9 68), A. T. Malkin (1803-88), John Ball (1818-89) and Sir Alfred Wills (b. 1828). Around Monte Rosa the Vincent family, Josef Zumstein (1783-1861) and Giovanni Guifetti (1801-67) did good work during the half century between 1778 and 1842, while in the Eastern Alps the Archduke John (1782-1859), Prince F. J. C. von Schwarzenberg, archbishop of Salzburg (1809-85), Valentine Stanig (1774-1847), Adolf Schaubach (1800-50), above all, P. J. Thurwieser (1789-1865), deserve to be recalled as pioneers in the first half of the 19th century. The English Alpine Club was founded in the winter of 1857-58 followed in 1862 by the Austrian Alpine Club (which in 1873 was fused, under the name of the German and Austrian Alpine Club, with the German Alpine Club, founded in 1869), in 1863 by the Italian and Swiss Alpine Clubs and in 1874 by the French Alpine Club. These clubs have explored the peaks, built huts, trained guides and published journals. The two sub-joined lists give the dates of the conquest of about 5o of the greater peaks (apart from the two climbed in 1358 and in 1492, see above), achieved before and after Jan. 1, 1858.

(I) Before Jan. I, 1858 : Titlis (1744), Ankogel 0762), Mont Velan (1779), Mont Blanc (1786), Rheinwaldhorn (1789), Gross Glockner (i800), Ortler (1804), Jungfrau (181I), Finsteraarhorn (1812), Zumsteinspitz (182o), Todi (1824), Altels (1834), Piz Linard (1835), Gross Venediger (1841), Signalkuppe (1842), Wetterhorner , Mont Pelvoux (1848), Diablerets and Piz Bernina (both in 185o), highest point of Monte Rosa Laquinhorn (1856) and Pelmo (2) After Jan. 1, 1858:-Dom (1858), Aletschhorn, Bietsch horn and Grand Combin (all in 1859), Grand Paradis and Grande Casse (both in 186o), Weisshorn, Monte Viso, Gross Schreckhorn, Lyskamm and Wildspitze (all in i86i), Dent Blanche, Monte della Disgrazia and Taschhorn (all in 1862), Marmolata, Presa nella, Pointe des Ecrins and Zinal Rothhorn (all in 1864), Matter horn, Ober Gabelhorn, Aiguille Verte and Piz Roseg (all in 1865), Langkofel (1869), Cimon della Pala (187o), Rosengarten (1872), Mei j e (1877), Aiguille du Dru (1878), Punta dell' Argentera (1879), Aiguille des Charmoz (188o), Aiguille de Grepon (1881) and Aiguille du Geant (1882).

a longer list of works on the Alps see the catalogue of the (English) Alpine Club Library, also A. Waber's Landes- and Reisebeschreibungen der Schweiz (1899, suppl. 1907) ; W. A. B. Coolidge, List of Works of W.A.B.C. (1912) and A. J. Butler, Some Notes on Alpine Books (1926).

For general works on the Alps see Sir W. M. Conway, The Alps (19o4, new ed. 191o) ; N. Zuntz and others, Hohenklima and Berg wanderungen in ihrer Wirkungen auf den Menschen (1906) ; H. Mettrier, Pierre d'Avity et des Alpes (1907) ; F. Briot, Les Alpes Francaises (1907) ; W. A. B. Coolidge, The Alps in Nature and History (1908) ; A. Dreyer, Der Alpinismus and der Deutsch-Oster reichische Alpenverein (1909) ; J. Perreau, L'Epopee des Alpes (1903- I2) ; A. H. M. Lunn, The Alps (1914) ; R. A. Cram, The Heart of Europe (1916) ; P. Stephani, Les Tunnels des Alpes (1919) ; D. W. Freshfield, Below the Snow Line (1923) ; S. Butler, Alps and Sanc tuaries of Piedmont and Canton Ticino (new ed. 1923) ; L. W. Collet, Les Lacs (1925) and Von O. Fluckiger, Der Schweiz, Natur and Wirtschaft (1926).

For Alpine legends see M. Savi-Lopez, Leggende delle Alpi (1889) and for Alpine poetry see E. A. Baker and F. E. Ross, The Voice of the Mountains (1905) ; A. von Haller, Die Alpen (new ed. 1902) ; H. E. Jenny, Die Alpendichtung in der deutschen Schweiz (19o5) ; J. Adam, Der Natursinn in der deutschen Dichtung (1906) ; G. W. Young, Wind and Hill (1909) ; H. Spender, In Praise of Switzerland (1912) ; A. H. M. Lunn, The Englishman in the Alps (1913) ; R. Thirlmere, Alpine and other Lyrics (1926) ; and for Alpine dialects see the great Swiss Dialect Dictionary ("Schweiz Idiotikon") in course of publication since 1881.

For the history of the Alps see F. Gribble, Early Mountaineers (1890) and Story of Alpine Climbing (1904) ; J. Grand-Carteret, La Montagne a travers les ages (2 vols., 1902-04) ; R. Reinhard, Passe and Strassen in den Schweizer Alpen (1903) ; W. A. B. Coolidge, J. Simler et les origines de l'alpinisme jusqu'en 1600 (1904) ; E. Hesselmeyer, Hannibals Alpeniibergang im Lichte der neueren Kriegs geschichte (1906) ; H. Pecout Etudes sur le droit prive des hautes vallees alpines de Provence et la Dauphine au Moyen-age (1907) ; H. Hartmann, Das Berner Oberland in Sage and Geschichte (1909) ; H. S. Wilkinson, Hannibal's March through the Alps (191I) ; D. W. Freshfield, Hannibal Once More (x914) ; J. Hess, Histoire Illustree de la region des Alpes-Maritimes (1915) ; A. Brun, Memoiren des alien Toni Brun, Berg f Uhrer von Flims (1917) ; A. Castaing, Histoire generale des Alpes Francaises des origines jusqu'a nos jours (1919) ; F. F. Tuckett, A Pioneer in the High Alps (Letters, etc., of F.F.T. 192o).

The following is a selection from descriptive works published since 19oo:—A. Guebhard, Notes sur les Alpes Maritimes (19oi) ; E. Whymper, The Valley of Zermatt and the Matterhorn and Chamonix and the Range of Mont Blanc (new eds. 1906) and Scrambles among the Alps (new ed. 1908) ; C. Rey, The Matterhorn (1907) ; D. Baud Bovv, La Meije et les Ecrins (1907) ; C. F. Wolff, Monographie der Dolomitenstrasse (1908) ; A. von Radio-Radies, Spezial-Fiihrer durch das Dachsteingebirge and die angrenzenden Gebiete (1908) ; P. Joanne, Savoie (1908) ; J. Solch, Studien caber Gebirgspdsse, mit besonderer Beriicksichtigung der Ostalpen (1908) ; C. Falke, Im Banne der Jungfrau (1909) ; H. Ferrand, Les Montagnes dauphinoises (1909) ; M. Meyer, Deutsche Alpen (191o) ; H. Ferrero, The Valley of Aosta (1910) ; S. H. Hamer, The Dolomites (191o) ; C. Schuster, Peaks and Pleasant Pastures (191I) ; H. Ferrand, Le Mont Blanc d'aujourd'hui (1912) ; J. Grande, The Bernese Oberland in Summer and Winter (191 I) ; H. Balavoine, Dans les Alpes et le Jura (191 I) ; E. Gaillard, Les Alpes de Savoie (1912) ; G. Tardieu, Les Alpes de Provence (1912) ; L. M. Davidson, The Gates of the Dolomites (1912) ; C. Rey, Peaks and Precipices (1914) ; C. Durier, Le Mont Blanc (1919) ; A. Frey, Die Osterreichischen Alpenstrassen in friiheren Jahrhunderten (1919) ; P. Arbos, La Vie Pastorale dans les Alpes Francaises (1922) ; R. Bagot, The Lakes of Northern Italy (1924) ; J. Vallot and others, Description Generale du Massif du Mont-Blanc (1924) ; H. Quigley, Lombardy, Tyrol, and the Trentino (1925) ; Gabriel Faure, The Dolomites (1925) ; E. L. Broadbent, Under the Italian Alps (1925) ; Blakeney, Peaks, Passes, and Glaciers (1926) ; G. Chabat, Les Plateaux du Jura Central (1927).

For accounts of travels in the Alps see P. H. Scheffel, Verkehrs geschichte der Alpen (1908) ; F. Harrison, My Alpine Jubilee (1908) ; C. L. Freeston, The High-Roads of the Alps (191o) ; W. Larden, Recollections of an old Mountaineer (11o) ; G. D. Abraham, Moun tain Adventures at Home and Abroad ; H. Ferrand, La Route des Alpes Francaises (1912) ; A. C. Knowles, Adventures in the Alps (1913) ; A. Fischer, Hochgebirgswanderungen in den Alpen and im Kaukasus (2 vols. 1913) ; L. Purtscheller and H. Hess, Der Hoch tourist in der Ostalpen (191o) ; R. Roschnik, Fiihrer durch die Julischen Alpen (1914) ; E. S. Salisbury, Rambles in the Vaudese Alps (1916) ; H. Aurenche, A Venise par les Dolomites (1919) ; H. Ferrand, Nice to Evian (1925) ; E. V. Lucas, Zigzags in France (1925) ; C. L. Freeston, Alps for the Motorist (1926) ; J. F. Muirhead, The Wayfarer in Switzerland (1926) ; S. H. Hamer, A Wayfarer in the Dolomites, and C. B. Waterlow, Routes des Alpes—a Motorists' Guide to the Great French Alpine Roads.

Some accounts of climbing and other Alpine sports are—J. Tyndall, The Glaciers of the Alps and Mountaineering in .86r (reprint 1906) ; E. Whymper, Scrambles in the Alps (reprint 1908) ; E. Zsigmondy, Die Ge f ahren der Alpen (1908) ; Sir W. M. Conway, The Alps from End to End (reprint 191o) ; G. D. Abraham, On Alpine Heights (1919) ; G. W. Young, Mountain Craft (1920) and G. D. Abraham, Swiss Mountain Climbs (reprint 1926) .

There are a large number of excellent guide books for various parts of the Alps. These are revised periodically and so kept up to date. The most important are the following:—Karl Baedeker, Italy from the Alps to Naples (1909) ; Southern France (1914) ; Switzerland (1922) ; Tyrol and the Dolomites (1927) ; The Blue Guides, Muirhead's, Switzerland with Chamonix and the Italian Lakes (1923) ; Northern Italy (1924) ; The French Alps (1926). There are also several volumes of "Climbers Guides," written by Sir W. M. Conway and W. A. B. Coolidge. Valuable information can be obtained from the publications (that date from 1863) of the various Alpine clubs—English, French, Swiss, German and Austrian, Austrian, Italian, etc. All the countries which include Alpine districts have now issued excellent official maps based on recent surveys.

The most important works on the Geology and Tectonics of the Alps, all of which contain bibliographies, maps, photographs and sections, are:—Alb. Heim, Geologie der Schweiz (1916-1922) ; R. Staub, Der Bau der Alpen (1924) ; L. Kober Bau and Entstehung der Alpen (1923) and L. W. Collet, The Structure of the Alps (1927) ; and of individual papers mention must be made of E. Argand, Sur farc des Alpes Occidentales (1916) . For the question of the relation to other regions see E. Suess, Das Antlitz der Erde (1885, English trans. 1904) ; L. Kober, Der Bau der Erde (1921) ; E. Argand, La Tectonique de i'Asie (Congres Geol. Internationale [1922]).

Recent detailed geological maps are published for many parts of the Alps (see L. W. Collet, The Structure of the Alps, 1927) and tectonic maps and sections are by E. Argand, Les Nappes de Recouvrement des Alpes Occidentales (1911) and R. Staub, Tekton ische Karte der Alpen (1923), with sections (1925).

Important works on Glaciology Penck and E. Brackner, Die Alpen im Eiszeitalter (1909) ; J. Bayer, Der Mensch im Eiszeitalter (1927) ; H. Gams and R. Nordhagen, Postglaziale Alimaanderungen Works on Alpine Flora are:—H. Christ, Das Pfianzenneben der Schweiz (1882) ; R. von Wettstein, Die Geschichte unserer Alpenflora (1896) ; the best book of coloured plates is the Atlas der Alpenflora (5 vols. end ed. 1897) ; Engler, Die Pfianzenf ormationen, and die planzengeographische Gliederung der Alpenkette (19o1) ; Chodat and Pampanini, Sur la distribution des plantes des alpes austro-orientales (Geneva, 1902) ; Jerosch, Geschichte and Herkunft der schweizer ischen Alpenflora; eine (Jbersicht caber den gegenwdrtigen Stand der Frage (1903) ; W. A. Clark, Alpine Plants (1907) ; Schroter, Das Pflanzenleben der Alpen (Zurich, 1908) ; H. Correvon and P. Robert, La Flore Alpine (Iwo) ; E. A. N. Arber, Plant Life in Alpine Switzer land (1910) ; G. Flemwell, The Flower-Fields of Alpine Switzerland (191 I) ; H. Correvon, The Alpine Flora (1912) ; C. L. Maynard, An Alpine Meadow (1912) ; J. Hoffmann, Alpine Flora (1925) ; W. B. Wright, Alpine Flowers and Rock Gardens (1925).

The classic of Alpine Zoology is F. von Tschudi's Das Tierleben der Alpenwelt. See also zoological section, by K. W. von Dalla Torre, of Anleitung zu wiisenschaftlichen Beobachtungen auf Alpenreisen; V. Fatio, Faune des vertebras de la Suisse (5 vols., 1869-1904) ; F. Zschokke, Die Tierwelt der Hochgebirgsseen (19oo) ; also C. Zeller, Alpentiere im Wechsel der Zeit (1892) . (J. I. P.)

alpine, zone, nappe, mont and pass