322 ORIGIN OF CRYSTALLINE ROCKS. [XIII. 



recall that the author had formerly expressed the belief " that pseu- 

 domorphism will soon constitute one of the most important chap- 

 ters in geological treatises." (American Journal of Science (1), 

 XL VIII. 66.) That Professor Dana has receded from the extreme 

 views on this subject which he maintained from 1845 to 1858, and 

 which I have constantly opposed, seems probable ; but until he 

 formally rejects them, the student of geology will not unnaturally 

 suppose that he still gives the sanction of his authority to the 

 doctrine which he so long taught without any qualification, but 

 now repudiates, that " metamorphism is pseudomorphism on a broad 

 scale." 



[In the Neues Jahrbuch fur Mineralogie for November, 1872 

 (page 865), appeared a note from the venerable Carl Friedrich Nau- 

 rnann (who has since died at an advanced age), in which he com- 

 ments upon my interpretation of his letter to Delesse. He begins 

 by saying that I have, in my address in 1871, cited some passages 

 from that letter, of which he then proceeds to repeat the substance, 

 and adds : " Although I am still strongly opposed to the excesses 

 of the metamorphic doctrine, I cannot explain how Professor Sterry 

 Hunt can, from the extracts of my letter to Delesse, conclude that 

 I regard those cases of pseudomorphism upon which the theory of 

 metamorphism is grounded as in great part only examples of asso- 

 ciation and development, and also as a result of a simultaneous and 

 original crystallization, and that my view is identical with his own, 

 which he first put forth in the year 1853." 



Upon this I have to remark that, instead of citing in my address 

 extracts from his published letter to Delesse, I gave therein a trans- 

 lation of the whole letter, with the exception of the first three lines, 

 which are, however, given above, with some other extracts, in my 

 reply to Dana's criticisms. From this language I conclude that 

 Naumann knew my address only through these misleading criticisms 

 and my reply thereto. In the next place, it is not clear what were 

 the excesses of the metamorphic doctrine which he still condemned 

 in 1872. He, as we have shown from his Lehrbuch (ante, page 294), 

 regarded gneisses and similar rocks as, for the most part, in some 

 unexplained way, of plutonic origin, though he admitted their pro- 

 duction in certain cases by the alteration of sediments, agreeable to 

 the Huttonian view of diagenesis ; while in the letter above men- 

 tioned he characterizes as erroneous the very different notion that 

 all " gneisses, amphibolites, etc.," are " the results of metamorphic 

 epigenesis." From his language in 1872, however, it would appear 



