Naumann on Primitive Formations, 263 



might combine with argillaceous matters to produce feldspar and 

 mica. These observations were the complement of ray own, and 

 both together showed the agency of heated alkaline waters to be 

 sufficient to effect the metamorphism of sediments, by the two 

 modes just mentioned ; namely, by molecular changes, and by 

 chemical reactions. 



Following upon this, Daubr^e observed that the thermal spring 

 at Plombieres, at a temperature of 160° F., had, in the course of 

 centuries, given rise to the formation of zeolites, and of various 

 other crystalline silicated minerals, among the bricks and cement 

 of the old Roman baths. From this, he was led to suppose that 

 the metamorphism of great regions might have been effected by 

 hot springs; which rising along certain lines of dislocation, and 

 thence spreading laterally, might produce alteration in strata near 

 to the surface; while those beneath would, in some cases, escape 

 alteration. In this way, would be resolved the great difficulty 

 urged by Naumann against the theory of metamorphism by heat 

 from below; namely, that in descending, a certain plane, some- 

 times limits the metamorphism, and separates the altered strata 

 above from the unaltered ones beneath, without any apparent 

 transition between the two. 



Daubree's ingenious hypotheses of metamorphism by hot 

 springs, in some instances meets this difficulty ; but while undoubt- 

 edly true in certain cases of local alteration, it seems utterly 

 inadequate to explain the complete and universal metamorphism 

 of areas of sedimentary rocks, embracing many hundred thousands 

 of square miles. On the other hand, the study of the origin and 

 distribution of mineral springs, shows that the alkaline waters, 

 whose action in metamorphism I first pointed out, and whose 

 efficient agency Daubree has so beautifully shown, are confined 

 to certain sedimentary deposits, and to certain stratigraphical 

 horizons; above and below which, waters totally unlike in charac- 

 ter, are found impregnating the strata. This fact seems to offer 

 a simple solution of the difficulty advanced by Naumann, and a 

 complete explanation of the theory of metamorphism of deeply 

 buried strata, by the agency of ascending heat; which is operative 

 in producing chemical changes only in those strata in which 

 soluble alkaline salts are present See farther on this subject, the 

 Canadian Naturalist^ vol. iv. page 414 ; the Quarterly Journal 

 of the Geological Society of London^ for 1859, page 488 ; and the 

 Report of the Geological Survey of Canada for 1853-66, page 477. 



