SALMON — RESEARCHES ON PSEUDOMORPHS. 



15 



substance, organic or inorganic, with the mineral which has replaced 

 it, permits us immediately to recognize and understand its metamor- 

 phism ; moreover, as the minerals and organic bodies have a gene- 

 rally constant form and composition, their metamorphism may be 

 much more accurately denned 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 Dechen, Suckow, Noggerath, W. Stein, Fcetterle, 

 Scacchi, Delafosse, Descloizeaux, Roth, Wiser, Von Zepharovich, 

 Nauck, Tamnaw, De Carnall, C. Von Haiier, Foster, Whitney, Jack- 

 son, Fowler, Websky, G. Brush, Smith, Shepard, Broun, Vinkler, 

 Volger, Hessel, Oppe, Fr. Sandberger, Dieffenbach, Schiiler, Credner, 

 Gutberlet, Dauber, Beck, Carius, Greg, W. G. Lettsom, Fox, Sock- 

 ting, Veibye, Forchhammer, Von Rath, Kjerulf, Von Richthofen, 

 Gergens, Richter, Girard, Jensch, Heffter.* 



Difficulties of distinguishing between 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 great difficul- 



* The publications relative to pseudomorphism have been so multiplied 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. Kallmann, Haidinger, G. Bischof, Dana, Kenngott, &c. 



