Physical and Chemical Behavior of Solids. 227 



(6*5-7'5). The tests, which were made with approximately 

 equal final loads and under ordinary conditions of temperature, 

 showed in general that the harder the mineral the less plastic 

 it is ; the hardest of the minerals were reduced to powder which 

 did not weld together again. The softer minerals showed 

 marked change of shape but appeared as coherent blocks often 

 traversed by series of fissures : in the regions of greatest defor- 

 mation they had become translucent or even nearly opaque, 

 and in the case of fluoiite there was moreover a marked change 

 of color. The compression produced some twinning in the 

 iceland spar, and in the diopside crystals it developed a series 

 of polysynthetic twin lamellae. 



Adams also worked with several rocks — marble* from 

 Carrara, several limestones, dolomite, and biotite granite — and 

 found that their behavior is altogether analogous to that of the 

 minerals. The softer rocks are readily deformed, the move- 

 ment taking place in part by distortion of the mineral grains 

 and in part by the development of a cataclastic structure, but 

 in the main they tend to crumble to powder. 



Precisely similar investigations had been published some 

 years earlier by Rinne,f whose observations are entirely con- 

 cordant with those of Adams; the comparatively soft rock salt 

 and sylvite (KCP) were deformed into translucent blocks, 

 nearly free from cracks and fissures. 



Adams and Coker;]; have made similar tests with marble at 

 temperatures of 300° and 100°, and also with marble at 300° 

 in presence of water. Their observations show that the flow 

 takes place with greater ease at the higher temperatures ; its 

 character is identical with that observed at ordinary tempera- 

 ture, and is not affected appreciably by the presence of water. 

 They found moreover that the compressive strength of de- 

 formed marble depends upon the rate of deformation and the 

 temperature, being greatest when the deformation is produced 

 slowly and at higher temperatures, and increases to some 

 extent if weeks or months intervene between the deformation 

 and the test. 



These observations can all be coordinated satisfactorily with 

 one another, and with the observations on the relative ease of 



* Cf . also : Frank D. Adams and J. T. Nicolson, "An Experimental Inves- 

 tigation into the Flow of Marble," Phil. Trans. Roy. Soc. London, 

 A, cxcv, 363-401 ; F. D. Adams and E. G. Coker, "An Investigation into the 

 Elastic Constants of Rocks, especially with Reference to Cubic Compressi- 

 bility," Carnegie Institution of Washington. Pub. No. 46, 1906. 



t F. Rinne, "Beitrag zur Kenntniss der Umformung von Kalkspathkrys- 

 tallen und von Marmoi- unter allseitigem Druck," Neues Jahrbuch fur Min., 

 1903, i, 160-78; "Plastische Umformung von Steinsalz und Sylvin unter 

 allseitigem Druck," ibid., 1904. i, 114-22. 



%F. D. Adams and E. G. Coker, "An Experimental Investigation into the 

 Flow of Rocks. I. The Flow of Marble," this Journal (4), xxix, 465-87, 1910. 



