Adams dh Coker — The Flow of Marble. 467 



make up the rock. The percolating waters, it is held, tend to 

 dissolve material at those points where the pressure is greatest, 

 and to redeposit it where the pressure is wholly or partially 

 relieved ; the movements thus being accompanied by a more 

 or less complete recrystallization of the whole rock. Moisture 

 would thus be a necessary factor in all rock folding or contor- 

 tion, and recrystallization the essential feature of the phe- 

 nomenon. The deformation of a body of dry rock would be 

 impossible. 



An experimental study* of the subject was undertaken 

 some years since, the rock selected being Carrara marble. The 

 investigation showed that in the case of this rock plastic 

 deformation could be brought about by the action of pressure 

 alone, that heat made the rock more plastic, and that under 

 the conditions of the experiments, the presence of water 

 exerted little or no influence in thig respect. 



By this it is not meant to imply that when rocks are folded 

 in the earth's crust solution and redisposition do not play a 

 very important role. These processes undoubtedly are at 

 work and are widespread in their action. It is quite possible 

 that they are the most important agencies in the folding and 

 flow of rocks. 



The experimental study showed, however, that the presence 

 of water was not an essential factor in the development of 

 flow, in the case of marble at least, and that under the experi- 

 mental conditions, that is to say with the deformation carried out 

 in days, weeks, or at most in a few months, instead of being 

 extended over long periods measured by years or centuries, the 

 deformation of the marble took place quite independent of 

 solution. 



It showed f urthermore4hat the structures displayed by highly 

 contorted marbles in many parts of the earth's crust are identi- 

 cal with those produced under the experimental conditions and 

 that they have been developed by the same agencies. 



As the subject seemed to be one worthy of further study, 

 the work was continued under a grant from the Carnegie 

 Institution of Washington, and as the investigation went 

 forward it was found to be necessary to follow out several 

 separate lines of research. 



The amount of cubic compression which rocks undergo 

 when submitted to pressure from every side was first investi- 

 gated, all rocks of course being subjected to such compression 

 before deformation. f 



* Adams, F. D., and Nicolson, J. T. — An Experimental Investigation into 

 the Flow of Marble ; Phil. Trans. Eoyal Soc., London, Series A, vol. cxcv, 

 pp. 363-401. 



f Adams, Frank D., and Coker, Ernest G. — An Investigation into the Elas- 

 tic Constants of Eocks, more especially with reference to Cubic Compressi- 

 bility ; Publication of the Carnegie Institution of Washington, No. 46 

 (Eesume in this Journal, Aug. 1906.) 



