1874.] -^'-' [Genth. 



my paper, but liad also examined the extensive collection of specimens upon 

 wliich my conclusions toere based, and that — all the phenomena in question 

 are nothing more than examples of association and envelopment, and that 

 the corundum-bearing veins had their parallels in the granitic veins with 

 beryl and tourmaline in the White Mountain rocTcs, and the calcareous 

 veinstones with apatite, pyroxene, phlogopite and graphite of the Laurentian 

 roclca. 



I may be permitted to say a few words in reply to Dr. Hunt's asser- 

 tion, that I had fallen into errors and had been led to wholly untenable 

 conclusions. 



When I had the good fortune to obtain a few years ago the first real 

 pseudomorph after corundum — the spinel from India, and afterwards 

 brought together numerous specimens of analogous alterations, showing 

 from the same locality crystals of corundum without any, and others re- 

 presenting all stages of alteration from a thin coating to the complete 

 disappearance of every vestige of corundum, and when I proved that 

 such changes have resulted in the conversion of corundum into about 

 two dozen mineral species ; I could not understand how any unpreju- 

 diced mind could arrive at any other conclusions, but that these extraor- 

 dinary occurrences which I have described, were the result of epigenic 

 pseudomorphism. 



This opinion has been adopted almost without exception by all who 

 have had an opportunity to examine my specimens, or who have studied 

 my paper. If Dr. Hunt differs from me, I certainly will not deny to him 

 the right to believe what suits his own notions, but when he boldly 

 charges me with having committed errors, I want better proofs than a 

 repetition of his views, with which we were familiar long ago. He cer- 

 tainly has not a single fact which could show the fallacy of my conclu- 

 sions, or he would have produced it. 



The corundum alterations have nothing in common with the Fontaine- 

 bleau crystals, or with stanniferous orthoclase ; the green and red tour- 

 malines from Paris, Me., or the beryls filled with orthoclase, or the zircon 

 and galenite filled with calcite, and cannot be explained rationally as ex- 

 amples of association and envelopment. 



To give strength to his statements, however, Dr. Hunt says that he 

 had "■ exainined^^ with me "<Ae extensive collection of specimens upon 

 which my conclusions were based.^^ When Dr. Hunt favored me with 

 a visit, I was in hope that he would examine my specimens, but his time 

 was so short that he saw only about one-third of them, and the "■exami- 

 nation^'' {! f) of these was finished in about five minutes. 



As to his last sentence, I must confess that I am unable to discover the 

 least parallelism between the corundum-bearing veins and the granitic 

 veins, with beryl and tourmaline, so common in the White Mountains, 

 and the calcareous veinstones with apatite, pyroxene, phlogopite and 

 graphite of the Laurentian rocks ; — but can see in the former nothing but 

 A. P. S. — VOL. XIV. 2b 



