274 Correspondence of J. Nickles. 
mineralogist sees a case of pseudomorphism even in a bone, phosphate of 
lime is not there found in its usual form.* Delesse makes a distinction 
between the original or substance pseudomorphosed, and the pseudomorphic 
e also distinguishes between pseudomorphism by alteration and 
pseudomorphism by displacement ; in the former the pseudomorphic 
pseudomorphic by displacem 
Delesse arranges among pseudomorphs, the forms by envelopment, 
so well described in Prof. Dana’s Mineralogy; also those phenomena 
which Naumann has called zoomorphosis and photomorphosis, produced 
when organic matter is replaced by a mineral substancet or by other 
matter in a different condition. ‘ 
Thus vivianite is sometimes developed in the interior of bones, 1m 
the shell of mollusks and in vegetables. Prof. Dana has seen it com- 
pletely replace the calcareous beak of belemnites, and I myself have seen 
it developed in human bones buried in ferruginous soil; a part 0 this 
phosphate had even crystallized in the form of vivianite (see this Journal, 
Pseudomorphism by alteration is more frequent than pseudomorphism 
by displacement, inasmuch as the mineral newly formed more frequently 
depends upon the more ancient. The same mineral may be pseudomor 
phic or pseudomorphosed, without the existence of any rule in this respect, 
this condition is often presented by such minerals as quartz, carbonate 
of lime and pyrites as they occur in nature. Delesse has found among 
105 pseudomorphic minerals and 119 pseudomorphosed minerals, oF 
224 in all, only 60 minerals that are both pseudomorphosed and pseu 
* Grasses and lichens belong to this class; the first owe their structure to silica, 
. 1 generali i 
: organ an 
“peel invariable type, very unlike those pseudomorphs or forms obtained 
To us the Saurian does not appear more different from a bird than the pare 
i 
morphic bodies arranged in this ease tis the author 0 
aram ism, who ine et ee a3 —_— : those pm 
which have a different composition and whi isomorphic but in different 
tems,” thus octohedrie AuOs We pabiiinoeple ae peinmnitie Bb0:, and prismatic AsO 
is paramorphic with octohedrie SbOs, &c,—(Laurent, Méthode de Chemie, 1854 
J 
Chemie et Pharmacie, t. xxxviii, p. 383), The ideas explain 97 
inted with the research? 
of Prof. Cooke on allomerism (see this Journal [2], xxx, p. 194, and Journal eck oe 
i iil of Prof. Cooke esp aoe 
well the difficulties met with by Delesse and other mineralogists. —— 
