The summits of mountains are sometimes divided by means of ravines, and these are to he considered as the smallest kind of valley. They form one extremity of the series of which the principal valleys in mountain groups form the other. The inequalities formed on the sum mits of mountains by these ravines or very small valleys, are denominated Caps. A mountain may have many caps, and the highest of these will be the top of the mountain.
17. Mountain groups may be considered under five different points of view, namely, according to their length, height, breadth, shape of the mountains, and their connection.
18. Mountain groups, in regard to their length, may be divided into principal. middle, and small.
A principal mountain group or Alpine country must be at least 130 mites loi,g. They occur but seldom. The Alps of Swi zlerland, the Pyrenees, and the Carpathians, of rrd exvmples of this kind.
middle-sized mountain group is from 40 to 130 miles in length. The greater number of European mountain groups belong to this class ; as examples, we may mention the Grampians, Hartz, the Reisen or Giant Aloant ins, &e.
A small mountain group is from 10 to 40 miles in length , as examples of it, we may mention the Forest of T..uringi,„ and the Bohemian Mittelgehirge.
19. Mountain groups. in regard to their height, are by aphers divided into high, of a middle height, and /ow A 'ugh mountain group is above 1000 toises or fathoms in ht igni. In Em almost the only examples of this class are, the Alps of Switzerland, Savoy, the Tyrol, and the Pyrenees. In the Alps of Switzerland, the highest point is Mont Blanc, which is about 15,646 feet above the level of the sea. The Jungfrau-horn is 13,730 feet above the level of the sea. In the Tyrolean Alps, the Gross Glockner reaches the height of 12,780 above the sea ; and the Ortler 15,430. In the Pyrenees, the highest point is Mont Perdu, which is 11,283 feet above the sea.
The elevations in South America are much more con siderable. Thus Antisana is 19,150; Tonguragua 16,579 ; Cotopaxi, according to Condamine, 18,890. Chimborazo, the most elevated summit in the new world, is 21,440 feet above the level of the sea.
The Himalya mountain in Asia is still higher, hav ing, in some instances, an elevation of 27,000 feet.
In Asia, Africa, and America, there appear to be many mountain groups that belong to this division.
20. Mountain groups of a middle height are from 500 to 1000 toises high. These are not uncommon. In Germany, the Erzgebirge,Fichtelgebirge,Riesengebirge, and Hartz, are of this magnitude. The highest point of the Fichtelgebirge is 3600 feet ; of the Hartz nearly the same. The Schneekoppe in the Riesengebirge is 4949 feet above the sea.
21. Low mountain groups are from 600 to 3000 feet high. These are the most numerous. The Schwarz \\Talc' or Black Forest, the mountains between Mora via and Bohemia, the Thuringer-Wald, Sec. belong to this class.
22. Mountain groups, in regard to the breadth of their base, are divided into massive and longish groups.
In massive mountain groups, the length and breadth of the base are nearly alike. The Swiss and Tyrolian Alps, and the Hartz, are of this kind.
In the longish mountain group, the length of the base is very considerable in comparison of the breadth. Of this kind are the Riesengebirge, Erzgebirge, Sec. The greater number of groups have this shape.
23. Mountain groups, in regard to the form of the mountains of which they arc composed, are divided into common, conical and alpine groups.
In the common mountain group, the individual moun tains of which the chains are composed are singly aggre gated, and are joined nearly to their summits.
In the conical mountain group, the individual moun tains of which the chains are composed, are also singly aggregated, but not joined together higher up than the decli%ity ; so that they appear conical.
In the alpine mountain group, the mountain chains are composed, not of single mountains joined together, but of groups of pyramidal-shaped mountains, in which groups a large pyramidal mountain has arranged around it a number of smaller mountains of the same figure.
24. Mountain groups, in regard to their connection, are either isolated, or several are joined together, form ing a chain of mountain groups. A chain of mountain groups extends from the Alps of Switzerland to Servia and Bulgaria : a similar range is formed by the Fichtel gebirge, which is connected with the Carpathians by the Alpine land or mountain groups of the Erzgebirge, Rie senbirge, Silesian and Moravian groups.