The stonework of the prehistoric builders excites the wonder and admiration of the beholder--admiration for the grand and beautiful simplicity of the Inca masonry, wonder as to the methods employed in its accomplishment. What the means were we do not know--at best we can only conjecture. The modern Indians--in fact, many of the upper class of Peruvians--prefer to explain it by magical methods, such as softening the rocks by rubbing them with the juice of some plant or fruit. Only the combined labor of hundreds of people, understanding the lever and the inclined plane, could have moved some of the huge rocks that form many of the walls. And moving them would be the easiest part of the work. How they succeeded in fitting these monoliths together, so that in places the joints are too fine for the naked eye to discern, is quite beyond the ken of the modern stone-worker. Formerly it was thought that the larger terraces were chiefly for defensive purposes; but the fact that these, as well as those more plainly agricultural in character, show the underlying strata of stones to be covered with fine agricultural soils that must have been brought from a distance, would indicate, according to some of our scientists, that these also were used to produce crops. The importance attached to agriculture can be understood from the fact that the majority of the terraces equal in fineness of masonry even the palaces of the Incas. Lacking timber, the Incas used stone as the chief building material, and, although they had not evolved the pure arch, they had learned to secure strength through the keying together of irregular blocks, and, as Dr. Bingham writes, “had developed many ingenious devices, such as lock-holes for fastening a bar back of the door; ringstones, which were inserted in the gables to enable the rafters to be tied on; and projecting cylinder stones, which could be used as points to which to tie the roof and keep it from blowing off.” [Illustration: RUINS OF TORONTOY Showing window, a projecting cylinder stone and lock-hole] Sculpture existed only in a rude form, and the decoration of Inca pottery did not equal that of the coast people. Their ceramic products are marked by simple and graceful lines, rather Grecian in effect, and of striking simplicity and utility. They had arrived at a high degree of skill in the manufacture of textiles, for the _llama_ and _alpaca_ provided them with excellent raw material. Although they were unfamiliar with refined methods of heat treatment, and so were compelled to sacrifice extra hardness and strength by increasing the tin content, they had learned the art of cold working, and produced many kinds of bronze implements. Some of these were of an excellent temper, and, together with obsidian knives, were used for trepanning. Inca methods of warfare, the use of slings and war clubs, naturally caused many wounds which could be relieved only by such operations.