~ 
98 J. D. Dana—Address of T. Sterry Hunt. 
unexplained, the above argument is poor support for the conelu- 
sion that they may not have occurred among silicates. | In this 
country no investigator of pseudomorphs has shown any leaning 
toward Mr. Hunt’s “more rational” view, and only one or two 
in Kur 
But, dahon the gradations in the transmutation have been 
in many cases seen, if not watched, so that direct observation 
Objection 2. That Mr. Hunt ane that Delesse sustains & 
“ theory of envelopment,” as a substitute for the ordinary “ — gy 
pseudomorphism,” and in this denies Delesse’s own statem 
From the example just mentioned it is plain what is here oa 
by envelopment—that it is mixture from cotemporaneous erystalli- 
zation. A considerable part of Prof. Hunt’s reply on the above 
point is an endeavor to make what Delesse says on envelopment 
in crystals a substitute for what he says on pse eudomorphism ; 
when the truth is reached by taking Delesse’s word for it, that 
his chapter on envelopment is nga to the omer yt a 
* In my former paper I u sent instead of the word sustains, the expressi 
author of. r. Hunt claims rightly that Ricdieater first brought out the ‘ee of a 
kind of envelopment. But, as is obvious above, the question of autho 
and this 
envelopment, as thus employed, is from him. Moreover, hier a) envelop 
ment” did not embrace Scheerer’s principle, which was that of isomorp. 
Mr. Hunt has it, in this Journal, Il, xvi, 217, Scheerer had in view a Sraltaneat 
crystallization of two is hous species, as, for instance, a se and anhydrous 
silicate (iolite and fahlunite in the same crystal being an example). But Delesse’s 
envelopment is a mixture; he has no allusion in his chapter on envelopment 
eat Aa prontiea Wes, n the associated m nt’s sentence in his Ad- 
dress (p. 47), claiming t that Delesse’s view in his work on Pecudcmocetans is 
identical with the view suggested by Scheerer,” is therefore at fault. Delesse, 
later in the volume, mentions Scheerer’s principle as a possible case under his 
Ma cas cg oN ome ollows: ‘If, as Scheerer has remarked, water acts as a 
in silica anhydrous and hydrous silicates may cry ther and be 
iomorphous "aud then follows the single example of the association of hornblende 
euphotide. 
+ Tholeess ak at the close of his chapter on pobnigcent © “Ce préambule 
t nécessaire 
Yenveloppement des minéraux étai pour | gence du pers 
. mo maintenant n 
rphisme, qui va convboupee” 
