208 J. P. Iddings — Origin of Quartz in Basalt. 



The applied stress imparts a permanent strain to the solid. 

 Viscous deformation is therefore accompanied by a residual 

 phenomenon, which manifests itself when the applied stress is 

 reversed or removed.* In liquids acted on by an electromotive 

 force, the analogous reaction is the reciprocating force of gal- 

 vanic polarization. 



Again, Clausing and Maxwell's theories mutually sustain each 

 other. For if the conception, that in a solid molecular config- 

 urations are present in all degrees of stability, is necessary to 

 explain the behavior of strained solid matter, it follows that 

 configurations of more pronounced instability will be present 

 in electrolytic systems. Conversely the fact that many solids 

 can be electrolyzed, points to the occurrence, in these, of a 

 very advanced state of molecular instability. To take the con- 

 crete example of glass, the same molecular mechanism which 

 at 300° promotes electrolytic conduction, when the solid is 

 influenced by electromotive force, manifests itself at low tem- 

 peratures as the viscosity of the solid under stress. 



Laboratory U. S. Geological Survey, Washington, D. C. 



Art. XX. — On the Origin of Primary Quartz in Basalt ;f 

 by Joseph P. Iddings, of the U. S. Geological Survey. 



A very interesting suite of volcanic rocks has recently been 

 collected in the Tewan Mountains, New Mexico, by Major J. . 

 W, Powell and Mr. "William H Holmes. 



The collection, though not a large one, embraces several 

 varieties of rhyolite and obsidian, with numerous forms of 

 andesite and basalt. The whole group constitutes a graduated 

 series of varieties, which range from rhyolite through andesite 

 to basalt, with two slight interruptions, at dacite and olivine - 

 bearing hypersthene-andesite. The general characters of the 

 minerals and of the rocks themselves correspond to those of 

 the volcanic rocks occurring throughout the Great Basing of 

 Utah and Nevada, and of those forming the volcanoes of the 

 Pacific coast, § and of the Republic of Salvador, C. A.|| 



Without entering upon the study of all of these rocks, a 

 description of which will be found in a forthcoming bulletin 

 of the U. S. Geological Survey, it is the intention of the 

 present paper to describe certain specimens of basalt which 



* Kohlrausch : Pogg. Ann., cxxviii, p. 419, 1866. 



f Read before the Philosophical Society of Washington, April 29, 1888, and 

 published by permission of the Director of the U. S. Geological Survey. 

 % Hague and Iddings. this Journal, vol. xxvii, June, 1884. 

 § Ibid., vol. xxvi, Sept., 1883. || Ibid., vol. xxxii, July, 1886. 



