SALMON — RESEARCHES ON PSEUDOMORPHS. 
15 
substance, organic or inorganic, witH the mineral wliicli has replaced 
it, permits ns immediately to recognize and understand its metamor- 
phism ; moi'eover, as the minerals and organic bodies have a gene- 
rally constant form and composition, their metamoi^hism may be 
much more accurately defined than that of rocks. 
The principal researches in pseudomorphism are due to Werner, 
Haiiy, Mohs, Langrebe, Freiesleben, Blum, Breithaupt, Haidinger, 
Mitscherlisch, Sillem, C. F. Naumann, G. Bishof, G. Rose, Haus- 
mann, Dana, Phillips, Kenngott, Scheerer, Rammelsberg, Plattner, 
Reuss, Hermann and Antoine Miiller, Leonhard, Zippe, Quenstedt, 
Glocker, Von Declien, Suckow, Noggerath, W. Stein, Foetterle, 
Scacchi, Delafosse, Descloizeaux, Roth, Wiser, Von Zepharovich, 
Nauck, Tamnaw, De Carnall, C. Von Haiier, Foster, Whitney, Jack- 
son, Fowler, Websky, G. Brush, Smith, Shepard, Bronn, Vinkler, 
A'^olger, Hessel, Oppe, Fr. Sandberger, Dieffenbach, Schuler, Credner, 
Gutberlet, Dauber, Beck, Carius, Greg, W. G. Lettsom, Fox, Soch- 
ting, Veibye, Forchhammer, Von Rath, Kjerulf, Von Richthofen, 
Gergens, Richter, Girard, Jensch. Heffter.* 
Difficulties of distingidsliing hetioeen Envelopment and Pseudo- 
morphism. — Before summing up the observed facts, it seems to me 
necessary to call special attention to certain deceptive appearances 
in pseudomorphism. 
In the first place, when two minerals envelope each other, if the 
enveloped mineral is completely destroyed and has disappeared, the 
enveloping mineral may easily retain its form ; there is then pro- 
duced a special metamorphism which arises from an incrustation, 
and which is visibly connected, in the most intimate manner, with 
envelopment. Now it sometimes happens that one mineral is sur- 
rounded by another which results from its alteration, which is 
especially what we observe in anhydrite and gypsum. Certain 
mineralogists have conversely presumed from this, that when two 
minerals envelope each other, the one results from the pseudomor- 
phism of the other. This may certainly be the case sometimes, but 
we may soon easily discover that it is not what occurs most usually. 
Moreover, when a mineral is crystallized, it frequently envelopes a 
very notable proportion of another mineral. The dominant mineral 
is not even that which gives to the mineral its crystalline form ; and 
generally it has been considered as pseudomorphic. Is there here, 
then, an envelopment ; or, on the contrary, pseudomorphism ? The 
solution of this question presents, as we shall see, very gTcat difficul- 
* The publicatioBS relative to pseudomoi'phism have been so multiphed of late 
years, that it was necessary to renounce giving a list of them here. They are to 
be found specially in the various publications of Germany, particularly the 
" Neues Jahrbuch" of Leonhard and Bronn ; " Jahresbricht" of J. Liebig, Her- 
mann Kopp, and Will ; Zeitschrift der Deutschen Geologischen Gesellschaft 
" Poggendorf Annalen ;" &c. Besides, they have been summed up in the classical 
works of R. Blum, C. F. Naumann, Haidinger, G. Bischof, Dana, Kenngott, &c. 
