“Experience has taught the operator the best shape of edge to apply the pressure to accomplish his object, and it has also taught him how to reach it in the simplest possible way. A spoon-shaped hollow on the top of a flattened log, or even a gutter or groove cut in it, furnishes the means of holding the flake firmly, the raised or high side placed in the hollow, the flat side up; with the ends of the fingers of his left hand pressed on it he holds it firmly, while with his right hand a downward pressure is given by the flaking-tool which breaks off chips with a fracture of about forty-five degrees from the flat surface, leaving the edge in the best possible shape for future work, and that is the condition of these cache flakes as they are found. “In old times, before the invention and introduction of planing and shaping machines to work metals, the first and most important lesson taught to the machinist’s apprentice was the use of the hand-hammer and cold-chisel. When an outer shell was to be removed from a metal casting and its surface left in condition to be finished by file or scraper, the smoothness and regularity of that surface was essential, not only for economy in working, but accuracy of the file finish. The apprentice was taught to hold his cold-chisel and so direct the strokes of his hammer that when a chip was started the chisel should hold to it, and not be allowed to cut too deep or slip and fly out, leaving a shape that is difficult to start a fresh cut without leaving ridges or cutting deeper, in either case causing additional labor for the finisher. “To a practical mechanic the examination of such a flint workshop as I have described—its waste chips to the partly worked flakes, the roughed-out blocks, and the finished implements—reveals a line of workmanship so clear that it can be followed to the production of the same results. [Illustration: FIG. 47. (S. 1–3.) Group of knives. From the collection of D. H. Kern, Allentown, Pennsylvania. Material: argillite and jasper. As to the use of flint knives, an interesting description is given by Pedro De Castaneda, who accompanied Coronado in 1541 to Quivira (Kansas); he states: “They cut the hide open at the back and pulled it off at the joints, using a flint as large as a finger, tied in a little stick, with as much ease as if working with a good iron tool. They gave it an edge with their own teeth. The quickness with which they do this is something worth seeing and noting.” ]