1875.] Ill [Hunt. 



Geology, I would gladly have stricken Prof. Dana's name from the 

 list of the defenders of the doctrine of which he had so long been 

 known as the champion, but which I have for the last twenty years 

 opposed. 



With regard to the numerous rock-transformations mentioned in 

 my address, I nowhere charged Prof. Dana with explicitly maintain- 

 ing them, although in view of his late earnest repudiation, alike for 

 himself and for others, of supposed alterations of rock masses, I re- 

 minded him that by the principles which he had formerly laid down 

 and defined, he was u logically committed to all the deductions as to 

 the changes of ro^ks which the transmutationist school has drawn 

 from the alterations of minerals," by following out the principles laid 

 down by him in 1845, and later in his Mineralogy of 1854, to their 

 legitimate conclusions. 



Prof. Dana proceeds, in the American Journal of Science for Feb- 

 ruary, 1875, to discuss the supposed conversion of granite or gneiss 

 into limestone, a notion which he says never came into his head, and 

 he accuses me (1) of stating that his " Mineralogy contains the fact 

 that calcite is sometimes pseudomorphous after quartz," and (2) of 

 charging him with maintaining the metamorphosis of granite or gneiss 

 into limestone. Now / have never anywhere asserted the one or the 

 other. I made no reference to his Mineralogy for the statement that 

 calcite is pseudomorphous after quartz, for which my authority is 

 the complete and elaborate memoir on Pseudomorphs, prepared by 

 Delesse, and published in the Annales des Mines in 1859 [(5) xvi], 

 to which I so frequently referred in my reply. We are there in- 

 formed that calcite is pseudomorphous after quartz, pyroxene, feld- 

 spar, garnet, etc. As a deduction from this, I cite the conclusions, 

 not of Prof Dana, but among others, of Messrs. King and Rowney. 

 These gentlemen, in the Annals of Natural History for 1874 * (Vol. 

 xin, p. 390), go so far as to say that, " the Tyree, Aker, and other 

 crystalline marbles, were originally silacid masses, and possibly much 

 of the so-called limestones occurring in the Laurentian of Canada 

 were in Archsean periods silacid members of true gneisses, diorites, 

 and other related rocks " — changed by a process of pseudomorphism. 

 In writing the above paragraph, I have before me Prof. Dana's 

 remarks in the American Journal of Science for February, 1875. In 

 the Proceedings of this Society for last October, the statement is 



1 This, in my volume of Essays, is by mistake printed " 1869." 



