Читать книгу Mechanics: The Science of Machinery - A. Russell Bond - Страница 6

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Then arose the art of breaking stones—breaking them skillfully, so as to form a jagged cutting edge. When man began to fashion tools of stone he left imperishable records of his craftsmanship which enable us to trace his progress in invention. The first finished tool we find was the fist hatchet—a stone roughly chipped to form a cutting edge and of convenient shape for the grasp of the hand. This primitive tool very slowly, through a period covering thousands of years, developed into all manner of cutting implements, some with handles of wood and bone. The ax head was followed by the spearhead and this finally by the arrowhead, showing that man had at last found a mechanical substitute for his muscles to hurl projectiles farther and with greater accuracy than he could throw them by hand.

We marvel at the resourcefulness and skill of the primitive savage in working so difficult a material as stone. It would baffle a modern mechanic to be required to shape a piece of flint into an arrowhead with no other tool than a piece of bone. He is so accustomed to using tools which are harder than the material they are intended to shape that he cannot conceive of making any impression upon a piece of flint with a piece of bone, to say nothing of a stick of hard wood, and yet such tools were used away back in the Stone Age. At first stones were roughly shaped by hammering them together. Then the artisans became more skilled. They discovered that certain stones could be chipped more regularly and evenly, and the art of flaking off chips of flint sprang up. Some specimens that belonged to ages long preceding that of recorded history are beautifully done. The spearheads are symmetrically shaped like a long narrow leaf, and the stone is evenly furrowed on both sides with a keen edge all around.

Not only did primitive artisans shape the stone implements with hammer blows, but they learned how to shape stone by pressure as well, using a tool that was relatively soft. It is not a very difficult matter to shape even so hard a substance as glass merely by pressure. If a piece of glass is laid on a table with its edge slightly overhanging that of the table, it is possible to chip off the overhanging edge by pressing a nail or even a hard stick of wood against this edge. A small flake of glass is thus removed, and, by continuing the process, arrowheads of any shape may be formed. The tool is placed not against the upper surface of the glass, but against the edge of the glass, so that only the lower surface of it is split or flaked off. Then the glass is turned over and a chip is taken off the opposite face.

In the Middle Stone Age we find the primitive craftsman equipped with a very complete assortment of stone tools. He had hammers, chisels, scrapers, drills, and polishing tools. He knew how to make useful household implements, such as spoons and ladles, out of bone. He polished his work and ornamented the implements with carvings of animals. Ivory pins and needles show that he had begun to make himself clothing from the skins of animals and that he sewed them together with thongs or tendons.

In the Late Stone Age he had learned how to make vessels of fire-baked clay. His axes were ground to a sharp edge, and he bored holes in the ax head to receive the ax handle. The Swiss lake dwellers built houses of wood and fitted them with all sorts of wooden furniture carved with stone tools. Among the remains of these interesting settlements may be found balls of clay which, from the fact that one of them was discovered with a spool of flax still attached to it, were evidently used as spinning “whorls” used for spinning flax into thread. Clothing of skins was giving way to or being supplemented with clothing of woven fabric.