XIII.] ORIGIN OF CRYSTALLINE ROCKS. 319 



Sciences and published in the Comptes Eendus of July 9, 1855. 

 This doctrine, which I have never repudiated, is reiterated in my 

 address last year (ante, page 291), and declared to include the poly- 

 meric isomorphism of Scheerer. 



Professor Dana next says that, in asserting that " the doctrine of 

 pseudomorphism by alteration, as taught by G. Rose, Haidinger, 

 Blum, Volger, Rammelsberg, Dana, Bischof, and many others, leads 

 them .... to maintain the possibility of converting almost any 

 silicate into any other," I have " grossly misrepresented the views 

 of at least Rose, Haidinger, Blum, Rammelsberg, and Dana" ; and 

 that I " complete the caricature " by this sentence, to be found in 

 my address : " In this way we are led from gneiss or granite to 

 limestone, from limestone to dolomite, and from dolomite to ser- 

 pentine ; or more directly from granite, granulite, or diorite, to ser- 

 pentine at once, without passing through the intermediate stages of 

 limestone and dolomite " ; " part of which transformations," says 

 Professor Dana, " I, for one, had never conceived ; and Rose, Hai- 

 dinger, Rammelsberg, and probably Blum, and the 'many others/ 

 would repudiate them as strongly as myself." The " many others," 

 as he rightly remarks, are "other writers on pseudomorphism," 

 among whom it would be unjust not to name their progenitor, 

 Breithaupt, Yon Rath, and Miiller, at the same time with Volger 

 and Bischof. According to Professor Dana, I " add to the misrep- 

 resentation by means of the strange conclusion that, because such 

 writers hold that crystals may undergo certain alterations in com- 

 position, therefore they believe that rocks of the same constitution 

 may undergo the same changes." This " strange conclusion " I 

 have always supposed to be Professor Dana's own. No one has per- 

 haps asserted it so clearly or so broadly as himself, and I shall there- 

 fore quote his own words in my justification. As early as 1845, 

 in an article entitled Observations on Pseudomorphism (Amer- 

 ican Journal of Science (1), XL VIII. 92), he wrote : " The same 

 process which has altered a few crystals to quartz has distributed 

 silica to fossils without number, scattered through rocks of all ages. 

 The same causes that have originated the steatitic scapolites occa- 

 sionally picked out of the rocks, have given magnesia to whole 

 rock-formations, and altered, throughout, their physical and chemi- 

 cal characters. If it be true that the crystals of serpentine are 

 pseudomorphous crystals, altered from chrysolite, it is also true, as 

 Breithaupt has suggested, that the beds of serpentine containing 

 them are likewise altered, though often covering square leagues in 



