THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Akt. XVII. — The Failure of Cavities in Crystals and 

 Rocks under Pressure; by P. W. Bbidgman. 



It is a matter of geological importance to know at 

 what depth in the earth's crust to expect open cavities. 

 The problem is one of some difficulty, involving the com- 

 plicated interplay of a number of factors. The character 

 of the stress, the nature of the material, the effect of tem- 

 perature and the element of time all must be considered. 

 An experimental study of the problem must begin, there- 

 fore, under as simple and well-defined conditions as pos- 

 sible. The best known experimental work has been 

 by Adams, 1 who subjected several minerals in the form 

 of blocks pierced with holes to high pressures exerted by 

 a steel plunger, and observed the pressure at which the 

 hole collapsed. The most obvious criticism of these 

 experiments is that the manner of applying stress is such 

 that its character cannot be at all precisely specified, 

 since the blocks were enclosed in shrunk-on jackets of 

 mild steel, which yielded as the block was distorted. In 

 an attempt to avoid this element of ambiguity I repeated 

 the experiment of Adams under conditions such that 

 the stress could be precisely specified. The cylinders of 

 rock containing a cavity were directly immersed in a 

 liquid, and stress applied by subjecting the liquid to a 

 high hydrostatic pressure. The collapsing stress so ob- 

 tained was considerably lower than that of Adams. 

 These results are not yet published, and will be briefly 

 described in the latter part of this paper. Their charac- 



1 F. D. Adams, J. Geol., 20, 97-118, 1912. 



Am. Jour. Sci.— Fourth Series, Vol. XLV, No. 268.— April, 1918. 

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