FLINTS. The term "Flints" is popularly used to denote implements made by men of the Stone Age, since in Europe flint and flinty materials were frequently used for that purpose.
Flint is a hydrated silica containing a varying amount of water loosely held in combination. When pure it is translucent, but impurities render it opaque and coloured, commonly either black or brown. Irregular flint nodules occur native in horizontal bands in chalk. Their origin is not clearly understood. In some cases it is undoubtedly due to marine organisms, such as sponges which, requiring silica for their growth, secrete it from the water.
Under certain imperfectly understood conditions the water in the flint seems to dry out, leaving on the exposed surface a thin film of white silica; this is known as the patina. When thick it gives a quite white appearance; when very thin the colour of the unchanged flint underneath shows through, so that a black flint will have a blue appearance. Flint itself is impervious to moisture, but the patina is porous. Thus when patinated flint occurs in gravels containing iron salts a • yellow staining, producing the well-known ochreous patina, results. Patinated flint embedded in peats also gets stained in a characteristic manner. Other varieties of staining called by fanciful descriptive names are of ten due to
the patina occurring in patches; thus we have the "toad-belly"
patina found in certain gravel
pits in East Anglia. Originally the
patinated surface is matt, but
where the object has been rolled
to some extent in soft sands or
loarns it becomes polished and
lustrous. The thickness of the
patina skin is partly a question
of the length of time during
which the weathering process has
operated but it naturally depends
on local conditions.
Flints are fractured easily and evenly in three ways, by per cussion, by pressure, and by temperature changes.
If a lump of flint is struck with a sharp blow concentrated at a point it breaks in such a way that a sort of cap can be lifted off, ex posing a double cone consisting of a broad angled cone resting on the truncated apex of another with steeper sides, there being a more or less sharply defined shoulder at the junction of the two. The cap which comes off naturally shows a hollow corresponding to these cones ; this is known as the negative cone. If the blow be delivered on the margin of the block a flake comes off showing a swelling near the point of impact. This is the so-called bulb of percussion; it is a partially formed cone. Around this bulb curved lines often appear on the flake, the concavity being always towards the apex of the bulb. This is important, as it sometimes happens in the case of an implement that the bulb has been removed sub sequently; but it is still possible to tell from these curved lines the direction from which the blow originally came. When the blow has been particularly intense, lines of fracture radiating from the point of impact also appear on the surface of the flake. They form radii to the curved lines. A small flake scar known as an eraillure is often seen on the surface of the bulb. This is not due to an attempt by prehistoric man to get rid of the bulb, but appears under certain conditions when a flake is struck off.
When a piece of flint is struck the force of the blow rapidly diminishes as it penetrates the dense medium. Should there be sufficient energy the fracturq set up by the blow, especially if it is struck diagonally outwards near the edge, will go right through the flint, a flake being removed. In this case the new flake-scar forms a clean angle where it meets the original surface of the flint. Should the blow be directed inwards, however, and only pene trate a short way into the flint the shattering will cause a fragment to break off which leaves ridges where the two surfaces meet. The first method is known as "feather-edge" flaking, the second as "resolved" or "step" flaking. Both were used as secondary working to toughen an edge and it is important to differentiate between the two, as "resolved" flaking is especially common in certain prehistoric cultures. In nature percussion flaking takes place by torrent action, where materials are hurled together, the result being chipping in all directions (flint thus knocked about shows innumerable minute incipient cones of percussion) ; by sea action, where not only is beach material hurled by the waves against larger fixed rocks and so chipped indiscriminately, but also is sucked back by the waves, so that any chance lump of flint embedded in the beach becomes in time much chipped in one direction by the passing pebbles; by ice action in glaciated regions.
This method of flaking flint was employed by prehistoric man and is still used by many primitive peoples, such as the aborigines of Australia. The aborigine takes a flake and, using the sole of his foot as a tough anvil, presses off little flakes along the margin, wherever he requires a sharp edge or desires to remove material. When a large flake is thus removed a bulb of pressure corresponding to the bulb of percussion appears, but it is, as a rule, considerably flatter. Usually flakes removed by pressure are small and scalelike. The resulting flake scar shows a large number of curved lines like those round a bulb of per cussion but generally rather flatter and closer together ; the con sequent reflection and refraction of light give a characteristic glassy or waxy appearance to an unpatinated pressure-flaked surface. In nature
results from the differential movement of gravels containing a large number of pebbles, such movement being often due to the slipping of a gravel bed down the side of a valley or the caving-in of a gravel bed owing to the solution of some underlying limestone deposit by underground streams. Thus pebbles get forced against one another; and in the latter case especially the pressure tends to come all from one direction, and so definite trimmed edges are produced.
Flint is a very poor conductor of heat but it expands with a rise of temperature. If then the ex terior is rapidly heated accommodation with the interior has to take place and there results a series of fractures. In this case no bulb of any sort occurs, but the fractured surface is covered with irregular closed rings. This method has been rarely used by man ; but thermal fractures, as they are of ten called, naturally caused by daily and seasonal changes in temperature, are of com mon occurrence. Frost action is especially characteristic. As a rule the surface of the flint becomes pitted and covered, as it were, with small hemispherical depressions. Under certain circum stances, too, prismatic bars of flint are found, the formation of these being analogous to that of the prismatic columns occurring in basalt. This is commonly known as "starch" fracture. At first sight these prismatic bars of flint might be taken for cores from which long narrow flakes had been removed. The complete ab sence of any bulb, coupled with an appearance characteristic of a thermally fractured surf ace but difficult to describe, at once distinguishes the two.
Mr. Reid Moir has attempted, by studying microscopically fractured surfaces of the flint, to distinguish between the various methods just described. With regard to the appearance of per cussion and pressure-flaked surfaces, a rough analogy may be made respectively with the surface of an apple cut by a knife, which is smooth, and that of an apple broken between the two hands, which is rougher and more hackly. No results, of course, can be obtained where the surfaces have been subsequently patinated.
It has become desirable to find criteria which will demonstrate whether a chipped object has been fashioned by man or by nature. As noted previously, when nature chips flint, whether by per cussion or pressure, the direction of the blow or pressure comes either from one or an infinite number of directions. What nature cannot do is to apply blows or pressure in two or three definite directions more or less at right angles to one another. Thus it is difficult for nature to knock off a flake and then trim one of the edges, an action involving two directions of blows ; and it is almost impossible to invoke nature as the agent if we find a specimen showing also a "prepared" platform on which the blow making the original flake had been struck, thus involving blows from yet a third definite direction. Nor would it have been more pos sible for nature to achieve this result did we postulate, as might more probably be the case, that the direction of the blows re mained constant and that the object itself was revolved once or twice through go° while receiving the blows.
Of course prehistoric man did not only make his tools of flint, chalcedony, chert, and other flintlike materials which furnish a sharp but brittle working-edge ; any kind of fine-grained rock was utilized. In these latter materials the fracture phenomena are similar to those of flint but are far less in evidence and much more difficult to identify. Such rocks, too, fracture irregularly, and it was not till Neolithic man adopted a grinding and polishing technique that a sharp regular edge was obtainable which had the added virtue of being tough.
Typology (q.v.) enables the prehistorian to group the various tools of the Stone Age into families according to their purposes or significant characteristics. The following is a summary of the more important of these tool families.
(sometimes called hand-axes or bouchers). Originally pear-shaped, boldly flaked, and with irregular edges ; later they become flatter and finer. An oval form also develops. In the latter case the edge shows the "S" twist characteristic of the Acheulean culture, where the top part of the tool is, as it were, slightly rotated upon the bottom half. The coup de poing family is especially characteristic of Lower Palaeolithic cultures.
The essential feature of the scraper is its sharp, convex edge. The chief varieties are side-scrapers, end-scrapers on blades or flakes, round-scrapers and core-scrapers. Side-scrap ers generally show the characteristic "resolved" flaking and be long to the Mousterian culture : the other varieties are post Mousterian. A special kind of core-scraper, in which the flakes removed are narrow and flat and rise fanwise to a well defined keel, is known as the keeled or tarte-scraper. It is a characteristic tool of the Middle Aurignacian culture, when such a fluting technique was common.
A true awl has a point prepared by careful trimming all round. Pseudo-awls which have the point trimmed only half way round, the under surface remaining a part of the general flake surface, are, however, common.
These form a varied family comprising a number of related types and others the connection of which is more obscure. Some types were doubtless used as lance-heads, e.g., the Mous terian Point and the Solutrean Laurel and Willow leaves, others, such as an important series which grade from what are known as Audi Points to Gravette Points were probably pointed knife blades. They have the side of the blade opposite the working edge blunted. This series enables us to subdivide the Aurignacian period into a number of stages.
The pigmy family includes several distinct types which are named, according to their shape, lunates, cres cents, triangles, trapezes, and pigmy scrapers. They are linked together by the fact that they formed the sharp working edges of finished tools, being hafted in various ways into handles made from some other material. The chipping seen on them is generally intended to blunt the edge which is actually to be hafted lest it should cut into or split the haft. Pigmies are found all over the world during widely different periods; they do not necessarily all belong to the same culture.
The Celt family is characteristic of Neolithic times, and a grinding and polishing technique is of ten employed in their manufacture. The original type when chipped only is not unlike the coup de poing at first view. But the carefully prepared sharp, convex working edge is at the broad end of the tool. Two evo lutionary series can be determined—one North European, the other West European. In the former the sides of the tool become squared and finally the upper and under surfaces become flat, a section through the tool being rectangular. In the latter the round squat original type becomes flatter and more chisel-like.
Many varieties of arrow-heads are known, some with wings and a central tang, others with wings or tang only ; some again are lozenge or leaf shaped. Not only can an evolutionary series be to some extent determined, but certain types only occur commonly in definite areas.
Bone tools, found associated with stone tools during certain periods, can also be classed into families. Harpoons for example form an important evolutionary series, starting with a primitive form where the barbs are hardly detached from the stem and developing through the detached single-barbed varieties to the double-barbed specimens. This series is important for subdividing the Magdalenian culture. Other important bone families are lance-heads, needles, and polishers.
See W. J. Sollas, Ancient Hunters (3rd ed., 1924), pp. 78 et seq.; M. C. Burkitt, Prehistory (2nd ed., 1925), chap. iv. (M. C. B.)
