The polishing of stone instruments was effected by rubbing the object in one of these cavities, in which probably a little water was poured, mixed with zircon or corundum powder, or perhaps merely with oxide of iron, which is still used by jewellers for the same purpose. Finds of numerous hatchets and other polished instruments, near the fragments of several polishing stones, have given rise to the supposition that at this epoch there were regular workshops in which weapons and implements were manufactured. In the kitchen middens were found flat hatchets, cut squarely at the edge; drilled hatchets variously combined with a hammer; double-edged axes and axe hammers,. pierced with a round hole in which the handle was fixed; beautiful spear heads in the shape of a laurel leaf, flat, and chipped all over with great art, which were evidently fixed to staves; poniards with handles sometimes covered with delicate carving; arrowheads of various shapes; chisels somewhat in the form of a quadrangular prism; small stone saws, in the shape of a crescent of which the inner edge, which was either straight or concave, was skilfully serrated; and various ornaments, as necklaces made of small pieces of amber, perforated and strung.

The instruments of stag's horn found in the valley of the Somme are also considered as belonging to this epoch. Particularly interesting relics are the pieces of polished flint half buried in a kind of sheath of stag's horn. The middle of the sheath is generally perforated with a round or oval hole, probably intended to receive a wooden handle. Sheaths have also been found which are not only provided with boars' tusks, but are hollowed out at each end so as to hold two flint hatchets at once. In the peat bogs of Abbeville have been discovered long bones belonging to mammals, as the tibia, femur, radius, and ulna, all cut in a uniform way either in the middle or at the ends, which were probably used as handles for flint implements. Near Pecquigny were found 19 boars' tusks split into halves, perfectly polished, and perforated at each end with a round hole. Through these holes was passed a string of some tendinous substance, the remains of which, it is said, were actually seen at the time of the discovery. In the caves of Ariege were found more than 20 stones which could only have been used for grinding corn.

According to John Buchanan, quoted in Lyell's"Antiquity of Man," the canoes which were found in the low ground on the margin of the Clyde at Glasgow, as well as other boats found at the bottom of the Swiss lakes, and in Belgium and France, were formed of a single trunk of oak, hollowed out with some blunt instruments, probably stone hatchets, assisted by the action of fire; for which reasons it is believed that these finds must also be classified as belonging to this epoch of the stone age. Finds of stone implements similar to those described have been made in the vicinity of Alton, Illinois; Jackson, Laporte, Sullivan, and Crawford counties, Indiana; in a shell heap on the bank of the Grand lake, Louisiana; in Paris, Wisconsin; and a few in Kentucky.-Metallic Age. The principal places of deposit of articles assigned to the bronze epoch of the age of metals are the lacustrine habitations of Switzerland and other parts of Europe, and the palustrine villages of northern Italy. Numerous finds of articles belonging to this epoch have also been made in other prehistoric human habitations, and in tombs, in Scandinavia, the British isles, France, Switzerland, and Italy. The Danish bronze swords had hilts firmly fixed to the blade by means of two or more rivets, and some of them were splendidly ornamented.

A bronze knife has been found with a handle in the form of a human figure executed with much fidelity. Several razors have been discovered, of which the blades were overloaded with ornaments. A very important find was made in 1861 in a tumulus in Jutland, of three wooden coffins, closed with movable lids, each of which contained a woollen cloak, a shawl, and a cap, and at the feet of the body two pieces of woollen material which seemed to be the remains of gaiters; each also held a sword, a knife, a bodkin, an awl, a pair of tweezers, a double button, a ball of amber, and a flint spear head. The shape of the sword and the knife indicates that the deposit belongs to the latter part of the bronze epoch. Various objects found in dwellings belonging to this epoch appear to have been religious symbols. Most of them have a shape bearing some relation to a circle, and many authors have attributed them to the worship of the sun. Crosses belonging to this and even to the stone age are also sometimes met with. The figure of a triangle found on various objects in bronze is also believed to bear some relation to certain religious ideas.-For the finds made in North America another epoch, of a special character, has to be presumed.

In 1847 Mr. Knapp discovered in the Ontonagon region on Lake Michigan, under an accumulation of earth, a vein of native copper, containing a great number of stone hammers. One of the diggings brought to light some great diorite hatchets which were worked by the aid of a handle, and also large cylindrical masses of the same substance hollowed out to receive a handle. Copper wrought into various utensils is found in the mounds all the way from Wisconsin to the gulf coast. Squier and Davis discovered in a mound near Chillicothe several round shells of mica 10 or 12 in. in diameter, overlapping like the scales of a fish. A find of 250 mica plates was made in the Grave creek mound. Many of the implements of these mound builders of the age of copper seem to have been wrought also of a ribbon-marked silicious stone. Squier and Davis found a deposit of obsidian arrowheads in Ohio, and Mr. Perkins one in Wisconsin.- The Iron Epoch. The finds assigned to this epoch consist of instruments of iron or bronze, or of iron combined with bronze instead of stone, articles of silver and lead, specimens of improved pottery, and coins.