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22.

The means of supporting the chamber from the cap is shown in Figs. 14 and 15; the apparatus being shown dismantled in Fig. 16. Two 3/8-inch steel rods, [[underline]] R [[/underline]], [[underline]] R [[/underline]], were threaded tightly by taper (pipe) threads into the cap, [[underline]] C [[/underline]], These rods were joined by a yoke, [[underline]] Y [[/underline]], at their lower ends, which served to keep them always parallel. Two collars, or holders, [[underline]] H [[/underline]] and [[underline]] H' [[/underline]]; free to slide along the rods [[underline]] R [[/underline]], [[underline]] R [[/underline]], held the chamber or gun, by three screws in each holder. The inner ends of the screws of the lower holder were made conical, and these fitted into conical depressions, [[underline]] c [[/underline]], Fig. 6(a), drilled in the side of the gun, so that the lower holder could thus be rigidly attached to the gun. This was made necessary in order that lead sleeves, fitting the gun and resting upon the lower holder [[underline]] H' [[/underline]], could be used to increase the mass of the suspended system. Three such sleeves were used, the two largest being moulded around thin steel tubes which closely fitted the gun. The rods [[underline]] R [[/underline]], [[underline]] R [[/underline]], were lubricated with vaseline. Two 1/8-inch steel pins were driven through the rods [[underline]] R [[/underline]], [[underline]] R [[/underline]], just above the  yoke [[underline]] Y [[/underline]], in order that the latter could not be driven off by the fall of the heavy chamber and weights when direct-lift was employed. 

In the experiments in which the chamber and lead sleeves were suspended ^[[by]] a spring, the latter was hooked at its upper end to a screw eye fixed in the cap [[underline]] C [[/underline]]. The lower end of the spring was hooked through a small cylinder of fiber. A record of the displacements of the suspended system was made by a stilus, [[underline]] S [[/underline]], Fig. 14, in the upper holder [[underline]] H [[/underline]]. This stilus was kept pressed against a long narrow strip of smoked glass, [[underline]] G [[/underline]], by a spring of fine steel wire. This strip of smoked glass was held between two clamps, fastened to a rod, the upper end of which was secured to the cap [[underline]] C [[/underline]], and the