THE LINEAR FORCE OF GROWING CRYSTALS 331 



through which it acts, actually exerts a pressure of the same 

 order of magnitude as the breaking load of the solid crystals, need 

 there be further hesitation in assuming that this is a force to be 

 reckoned with in engineering 1 or in geology ? 2 



SUMMARY 



In 1905 we showed by appropriate experimental evidence that 

 a single crystal immersed in its own saturated solution, and growing 

 by reason of the potential supersaturation of the solution resulting 

 from evaporation will lift a weight placed upon it. This observa- 

 tion has been confirmed in the present paper. 



In 19 13 Bruhns and Mecklenburg placed two crystals in a similar 

 saturated solution, one loaded and the other free, and noted that the 

 load upon the one crystal was not raised, although the free crystal 

 grew rapidly. From this experiment they were led to deny the 

 power of a crystal to lift a weight of foreign substance, although 

 admitting the power of the unloaded crystal to lift its own substance. 

 They appear to have overlooked in this conclusion the fact that the 

 solubility of the loaded crystal is for most substances greater than 

 that of an unloaded one, and also that this is a difference in degree 

 only, for the unloaded crystal also supports weight (its own). 



In consequence of this greater solubility, with an unloaded and 

 a loaded crystal in the same solution, the necessary condition of 

 potential supersaturation will be reached in the liquid adjacent to 

 the unloaded crystal before it is reached in the other, and the 

 growth of the unloaded crystal thereafter may keep the concentra- 

 tion below that necessary for the growth of the loaded crystal. 

 This appears to be the condition reached in Bruhns and Mecklen- 

 burg's experiment. If it happens, however, that the rate of growth 



1 Cf. the investigations of Dr. Hans Kuhle, "Die Ursache des Treibens der 

 Zemente," Tonindustrie Ztg., XXXVI (1912), 1331-34; and of Klein and Phillips, 

 "Hydration of Portland Cement," Technologic Papers of the Bureau of Standards 

 No. 43 (1914), PP- 5°, 56, 57- 



2 Cf. the recent observations of Stephen Taber, Virginia Geol. Survey Bull., 

 No. VII (1913), p. 222; also G. D. Harris, "Rock Salt, Its Origin, Geological Occur- 

 rences and Economic Importance in the State of Louisiana," Geol. Survey of 

 Louisiana, Bulletin No. 7 (1907), p. 75. 



