XIII. 1 ORIGIN OF CRYSTALLINE ROCKS. 321 



XVIII. 678.) The reader must now judge whose opinions it is that 

 are here denounced as erroneous, and whether Naumann was on 

 the side of Professor Dana, or, with Delesse, on the side of Scheerer 

 and myself. I insist the more strongly on this matter, because 

 Professor Dana not only declares that Delesse and Naumann have 

 always avowed the doctrines of the transmutationist school, and do 

 not in any way whatever countenance my views, but implies that I 

 have dealt unfairly with these authorities. 



Professor Dana says, " If there was any occasion for a notice of 

 my opinions, a critic of 1871 should have referred to the formal 

 expression of them in my Manual of Geology, first published in 

 1863. The reader will there find the diagenesis of Gumbel, which 

 Mr. Hunt takes occasion to commend, .... with but a brief allu- 

 sion to pseudomorphism." The doctrine of diagenesis, it is hardly 

 necessary to say, I have never attributed to Gumbel, nor does he 

 claim it. It is the old doctrine of Hutton, Playfair, and Boue, is 

 taught by Bischof (Chemical Geology, III. 318, 325. 342), and per- 

 vades my papers of 1859 and 1860, already referred to. But while 

 it has been generally admitted that what, in my address, I have 

 called the first class of crystalline rocks (consisting chiefly of quartz 

 and aluminous silicates) might result from the molecular re- 

 arrangement of the elements of clay and sand-rocks, I maintained 

 in those papers that what I have called the crystalline rocks of the 

 second class (in which protoxide-silicates predominate) have been, 

 generated, by a similar process, from aqueous deposits of chemically 

 formed silicates. This view, advanced by me in 1860, having been 

 adopted by Delesse and by Gtinibel to explain the origin of the 

 various magnesian silicated rocks hitherto generally regarded as 

 the product of epigenesis, the latter has proposed to designate the 

 process as diagenesis ; a term which I adopt, as one well fitted to 

 denote the generation of all kinds of crystalline rocks through a 

 molecular rearrangement of sedimentary deposits, of whatever 

 origin. Professor Dana, in common with most other geologists, 

 admits in his Manual of Geology the old conception of the pro- 

 duction by diagenesis from mechanical sediments of the rocks of the 

 first class, but in the case of serpentine and steatite declares them 

 to have been formed by epigenic pseudomorphism or chemical alter- 

 ation of pyroxenic and other crystalline rocks ; the origin of which 

 is by him left entirely unexplained. It is true that his allusions to 

 pseudomorphism in that volume are confined to very brief notices 

 on pages 704 and 710 ; a fact which is the more noticeable, when we 

 14* v 



