TL. S. Hunt on the Criticisms of Prof, Dana. 41 
Art. X.—Remarks on the late Criticisms of Prof. Dana; by 
T. Sterry Hunt, LL.D., F.R.S. 
In this Journal for February last (p. 86) Prof. Dana has 
criticized certain points in my address “On the Geognosy of 
the Appalachians and the Origin of Crystalline Rocks,” given in 
August, 1871, at Indianapolis, before the American Associa- 
tion for the Advancement of Science. I am charged by him 
with rejecting, for many mineral silicates, the view that they 
case we may say, with Prof. Warrington Smyth, that in these 
intermediate forms “lie the materials for a history ;” while we 
venture, with him, to express a doubt whether, from a series of 
Specimens supposed to show a transition from chrysolite to 
Serpentine, or from hornblende to chlorite, “we are obliged to 
Conclude that there has been, historically speaking, an actual 
transition from the one to the other.” [See his anniversary 
1867 |" as president of the Geological Society of London, in 
Prof. Dana says that Scheerer is the only one who shares my 
Peculiar views on this question. I have, however, asserted in 
and shall endeavor to make good my assertion. In his essay 
on P seudomorphs, published in 1859 [Ann. des Mines, V, xvi, 
317-392], Delesse begins his argument by remarking that since, 
'N Some cases, a mineral is found to be surrounded by another 
Clearly r sulting from its alteration (as for example anhydrite 
Y Sypsum), certain mineralogists have supposed that wherever 
one mineral encloses another there has been epigenesis or pseu- 
domorphous alteration, Such, he says, may sometimes be th 
case, but it is easy to see that it is not so habitually. A crys- 
