HIGH-PRESSURE PHYSICS — BRIDGMAN 



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sures have to be transmitted by soft solids and can be only approxi- 

 mately hydrostatic. Fortunately there are soft solids, such as tin or 

 preferably indium, of which the plastic shearing strength is low, so 

 that pressure fails to be hydrostatic by only a few percent. It is, 



Figure 3.— Diagram of apparatus by which pressures of 100,000 atmospheres can be real- 

 ized. The high-pressure vessel is completely immersed in a liquid (shaded), which is 

 itself subjected to pressure and thus supports it. The thrust on the high-pressure pistons 

 is determined by measuring the change of electrical resistance of the "grid" which re- 

 ceives the thrust. 



however, not so easy to find a solid insulator which is sufficiently 

 yielding at 100,000 atmospheres to be also a good pressure transmitter. 

 For every successive increase in the pressure range a price has to 

 be paid in a diminution in the size of apparatus, which in turn hmits 

 the sort of experiment that can be made. The vessel in which a 



