94} M. Keilhau''s Theory of Granite^ and other Roclcs. 



When we examine more closely the phenomena of these che- 

 mical and morphological formations, we are led to the conclusion 

 that the heat which is in operation in these processes, is of use 

 chiefly in hastening them, inasmuch as it imparts to them a 

 greater degree of intensity, and thus appears as an indispen- 

 sable cause. Where, therefore, in the example borrowed from 

 a metallurgical process, new combinations of copper and sul- 

 phur were, by the assistance of heat, induced in a space of a 

 few weeks ; there, according to the data afforded by various ob- 

 servations on Roman antiquities, which have undergone ana- 

 logous and still greater changes of composition, some thousand 

 years would have been requisite in order to produce such al- 

 terations at the ordinary temperature. 



It is quite evident that we must anticipate chemistry when 

 we are forced to rest on facts like these quoted, because che- 

 mists have hitherto bestowed too little attention on such phe- 

 nomena, inasmuch as all the materials furnished by that science 

 for our discussions consist of a knowledge of the composition 

 of crystals and mineral species. It would, first of all, be re- 

 quisite to prove if the well known fact of the formation of 

 crystals from expansible fluid bodies, could here be brought to 

 bear on the subject. The first glance even shews us that the 

 consideration of this phenomenon would only lead us into an 

 entirely unproductive field. We may take this opportunity of 

 mentioning an hypothesis, proposed at an earlier period, and 

 which may be quoted as an example of, so to speak, the despair 

 of clearing up the difficulties as to the unstratified mountain- 

 rocks. Among the efforts to unravel this great geological 

 riddle, the attempt was made to consider some at least, of 

 these formations, as the result of the condensation of aeriform 

 matter which was dispersed through the atmosphere, and 

 which was afterwards precipitated and assumed a solid form. 

 To follow up this idea any further would be but a waste of 

 time. 



There is another view which is of greater importance. The 

 opinion has been proposed, that emanations of substances which 

 are in a condition to crystallize, can, by penetrating solid bo- 

 dies, deposite crystals in them. As in discussing this subject 

 authors — to the injury of science — have been inclined to ex- 



