Hunt.] 110 [June 2, 



ceived by him, and that he did not doubt the other writers of the 

 school would repudiate them as strongly as he did. He, moreover, 

 reproached me with having falsely attributed to him the doctrine that 

 " metamorphism is pseudomorphism on a grand scale," and declared 

 that he had neither made the remark nor expressed the sentiment in 

 his Mineralogy of 1854. (Amer. Jour. Science, February, 1872.) 



Two questions were here involved, namely, the personal views of 

 Mr. Dana, and those of the school in question; but he began by 

 denying, alike for himself and for others, their well known and 

 avowed teachings. To all this I replied by showing that each one of 

 the alleged cases of rock-alteration had been expressly maintained 

 by one or more writers of the school. I showed, moreover, as re- 

 gards Prof. Dana, that he had repeatedly, from 1845 to 1858, asserted 

 that the various pseudomorphic changes maintained by Blum, Rose, 

 and others, were true, not only of individual crystals, but of great 

 rock masses ; that in his Mineralogy of 1854, he described the epi- 

 genic production of serpentine and other magnesian rocks as " a 

 process of pseudoarorphism, or in more general language, of meta- 

 morphism," and added, that the "subject of metamorphism, as it bears 

 on all crystalline rocks, and of pseu lomorphisra, are but branches of 

 one system of phenomena." I farther showed that his assertion 

 made in 1858, that " metamorphism is pseudomorphism on a broad 

 scale," was but a summing up and a reiteration of his teachings of 

 1845 and 1854, Prof. Dana now admits this language to be his own, 

 but pleads, in excuse, that the expression was a hasty one, which he 

 had so far forgotten as to be unwilling to believe himself to have 

 made use of it. To this point I shall return. 



In his Manual of Geology, which appeared in 1862, we find but 

 few traces of this doctrine; the origin of serpentine and steatite from 

 the alteration of pyroxene rocks is taught, but, with this exception, 

 the author is silent with regard to his late teachings on pseudomorph- 

 ism, and I am now blamed because I did not interpret this silence as 

 an evidence that he no longer held his former views. They were, 

 however, nowhere repudiated nor retracted, and students of his 

 Mineralogy might well be pardoned if, under these circumstances, 

 they continued to accept the formsr repeated and emphatic utterances 

 of Prof. Dana as his creed on the subject of rock-metamorphism. 

 I confess that I had never been led to suspect any change in his views 

 until after the publication of my address in 1871. Could I have de- 

 duced as much from the negative evidence afforded by his Manual of 



