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PROCEEDINGS OF THE AMERICAN ACADEMY, 



packing for the piston will make the principle clear. The piston P 

 pushes the plug A through the medium of the hardened ring R, 

 the cupped washer of soft steel, C, and the rubber packing B. The 

 liquid compressed is below A at L. The plug A is provided with a 

 stem which is long enough to reach into the ring R, but not long enough 

 to reach to the piston P. If now we consider the equilibrium of A, 

 we see that the fluid pressure over the lower end of A must be bal- 

 anced by the pressure exerted by the packing B on an area less than 

 that of A by the area of the unsupported stem. The result is that 

 the hydrostatic pressure in the packing B per unit area is always a 

 certain percentage higher than that in the liquid, so that the liquid can 



Fig. 1. 



Fig. 



Figure 1. Shows the general principle of the packing by which the pres- 

 sure in the packing B is always kept higher than that in the liquid at L. The 

 scale of the diagram is | actual size. 



Figure 2. Shows a common previous type of packing for high pressures. 

 The packing is compressed by a powerful screw into a confined space. This 

 packing leaks when the pressure in the liquid rises as high as that initially 

 applied with the screw. 



never leak past the piston. This principle is capable of manifold 

 modification and adaptation, but it will always be found that there 

 is somewhere an area unexposed to the action of pressure, so that the 

 hydrostatic pressure in the packing itself is always higher than that in 

 the liquid. 



It is instructive to compare this packing with that formerly used 

 for high pressures, by Amagat, for instance, up to 3000 kgm. His 

 packing is compressed initially by a powerful screw into a confined 



