234 METALLURGY OF CAST IRON.
a graduated wedge D, the thickness of the point at which it settled between the bars and frame being measured by a micrometer, as at V, Fig. 55. The bars were i inch square by 24 inches long and poured by top gates, as shown. The chill was obtained by breaking off a piece at the ends as shown at E, Fig. 55.
To obtain the hardness tests, the writer arranged a drill press, as shown in Fig. 53. A bicycle cyclometer was attached to the upper body of the frame, at F, and then a light sheet iron ring was bolted to the upper shaft G, with an arm as at H. This arm came in contact with the cyclometer at every revolution of the shaft G, and recorded the exact number of revolutions made in a stated time, by a watch held in the hands of the operator as seen at I. In order to apply a constant pressure of the drill J on the test piece K, a weight L was suspended from the lower arm M, by a wire, at a given distance from the end, as shown. Three revolutions of the shaft G, equalled two of the drill. The machine could be stopped in a second by a lever at M. The same ^-inch drill was used for all tests, testing the softer specimens first, and the harder ones last. The drill was kept of a uniform sharpness for the bars of each cast. The drill ran 60 seconds for each test and the speed of the shaft G varied from 35 to 37 revolutions. An average of 36 revolutions was allowed in computing the depth of the holes made in 60 seconds and recorded in column 7. The tests obtained by this drill press proved very satisfactory. To obtain the depth of the hole a wooden pin O, Figs. 54 and 55, was set into the drilled holes, as seen at P, and a steel pin R, pressed into the wooden pin on a level with the top of the test specimen, as shown at R. After the Fig. 49, are test specimens 2^ inches in diameter by 6 inches long. In casting these test specimens one was poured with a regular cupola metal, and the other with the metal after the phos-y, M. Hoskins, Harvard College, Havemeyer University, Henry Hiels Chemical Co., Isabella Furnace, Iron Gate Furnace, Iroquois Iron Co., Illinois Steel Co., Jefferson Iron Co., Kittan-ning Iron & Steel Co., C. A. Kelly Plow Co., Lebanon Furnace, Longdale Iron Co., Lackawanna Iron & Steel Co., Logan Iron........................ 16,720 " t-