The original model of the machine made 60 strokes per minute. In the machine that broke the stone I had increased the speed to 100 strokes per minute. In designing the successful machine I made the great jump to 300 revolutions of the cam-shaft per minute. This was done after much study of practical requirements. I observed carefully the speed of planing-machines. I had also the opportunity of witnessing the operation of the first wood-moulding machine, and was much impressed by the speed of the rotary cutters and the rapidity with which the work was turned out. I wanted a motion of 40 inches a minute for the stone table, which would make the output of the machine satisfactory; 300 revolutions would give this motion, the table advancing .133 of an inch at each blow. [Illustration: Side frame not shown, except Channels for Elevating Screws My First Mechanical Drawing. Longitudinal Section of my Stone-dressing Machine.] The machine contained six hammers, each 6 inches wide and weighing about 200 pounds, which ran in a suspended frame. The front member of this frame was a wrought-iron bar 6 inches square, with a projection on the lower side, as shown. At the ends this bar was first reduced to 5 inches square, the corners rounded to 1 inch radius, and mortised into cast-iron side-bars 4 inches thick, one of which is shown in the sectional view. Beyond these side-bars the wrought-iron bar was turned down to journals 3¹⁄₂ inches in diameter, which turned in the heads of large screws, one of which is represented. Beyond those journals it was further reduced to 2 inches diameter, and the ends threaded. These projections extended through slots in the main framing, and nuts on the outside provided with long handles enabled the whole to be bound fast in its position, when that had been determined.