206 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



in. (1.3 cm.). The piston was 



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The enlargement C, on the rod A, serves as a stop at either end *of 

 the stroke, which in this case was | 

 made at least ^ in. (1.3 cm.) longer 

 than the hole in the cylinder in which 

 it fits, so that at no part of the stroke 

 is any part of the hole empty. This 

 insures the constancy of the crack 

 through which leak occurs, and ought 

 to increase the accuracy of the results. 

 To diminish friction between piston 

 and cylinder the piston was kept in 

 slow rotary motion through 30° by a 

 rod inserted in a hole in the enlarge- 

 ment C. The rod was driven by a 

 small motor. 



The purpose of the shoulder at the 

 bottom of the cylinder will be plain 

 on an inspection of Figure 2. The 

 disposition of packing, shown by the 

 shading, is one that has proved itself 

 serviceable in other high pressure 

 work. It is obvious from the figure 

 that the pressure on the outside of 

 the cylinder mentioned above as pre- 

 venting the enlargement of the crack 

 between cylinder and piston is the 

 pressure exerted by this packing. 

 The portion of the cylinder over 

 which it acts may obviously be varied 

 by varying the quantity of packing. 

 With dimensions of cylinder, etc., 

 shown above, \ in. (0.64 cm.) thick- 

 ness of packing proved satisfactory. FlGURE g Det& ^ giying the ^ 



To go into this question of pack- me nsions of the cylinder, 

 ing at any length would be beyond 



the scope of this paper. Neither can any description be given here 

 of the apparatus with which the pressure was produced. Briefly, 

 pressure was produced by a small piston pushed by hydrostatic pres- 

 sure on a larger piston. Pressure was transmitted to various parts of 

 the apparatus by heavy steel tubing. It is hoped that methods of pro- 

 ducing high pressures may be made the subject of another paper. 



The cylinder (E, Figure 1) was turned in a lathe from a rod of 



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B 



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