T. S. Hunt on the Criticisms of Prof. Dana. 47 
resentation by means of the strange conclusion that because 
such writers hold that crystals may undergo certain alterations 
in composition, therefore they beleve that rocks of the same 
constitution may undergo the same changes.” This “strange 
conclusion” I have always supposed to be Prof, Dana’s own, 
0 one has perhaps asserted it so clearly or so broadly as him- 
self, and I shall therefore quote his own words in my justifica- 
tion. As early as 1845, in an article entitled ‘‘ Observations on 
Pseudomorphism,” [this Journal I, xlviii, 92] he wrote: “The 
Same process which has altered a few crystals to quartz has dis- 
tributed silica to fossils without number, scattered through rocks 
of all ages. The same causes that have originated the steatitic 
Scapolites, occasionally picked out of the rocks, have given 
magnesia to whole rock-formations, and altered, throughout, 
their physical and chemical characters. If it be true that the 
crystals of serpentine are pseudomorphous crystals, altered from 
chrysolite, it is also true, as Breithaupt has suggested, that the 
2 process of pseudomorphism, or in more general language, of meta- 
morphism; the sa i i 
ism, as it bears on all erystalline rocks, and of pseudomorphism, 
are but branches of one system of phenomena.” If there could be 
honing especially the first one, in which, he says, “‘ metamor- 
wm ws spoken yr as pseudomorphism en a broad scale.” {This 
Journal, If, xxv, 445}. 
Prof. Dana, when in his last criticism of me, fourteen years 
after the one just uoted, he reproaches me with having charged 
him with hol ing the doctrine that “regional metamorphism is 
Pseudomorphism on a grand scale ;” and declares that he makes 
no such remark, neither expresses the sentiment in his Mineral- 
By of 1854, 
