=I 
einai. pie A T 0. Fay ce Soh E ee A E T E 
ORIGIN OF CRYSTALLINE ROCKS. 495 
have never found its way into the science. I think, with you, that 
the enyelopment of two minerals is most generally explained by 
a contemporaneous and original crystallization. Secondary envel- 
opments, however, exist, and such may be callec pseudomorphs 
or crystalloids, if they reproduce exactly the form of the crystal 
enveloped, whether this last still remains, or has entirely disap- 
eared.” * 
It is unnecessary to remark that the view of Delesse and Nau- 
mann, viz. : that the so-called cases of pseudomorphism, on which 
the theory of metamorphism by alteration has been built, are, 
for the most part, examples of association and envelopment, and 
the result of a contemporaneous and original crystallization, — is 
identical with the view suggested by Scheerer, and generalized by 
myself long before, when, in 1853, I sought to explain the phe- 
nomena in question by “the association and crystallizing together 
of homologous and isomorphous species.’ 
Later, in 1862, I wrote as follows :— 
‘‘Pseudomorphism, which is the change of one mineral species 
into another, by the introduction or the elimination of some ele- 
ment or elements, presupposes metamorphism (i. e., metamorphic 
or crystalline rocks), since only definite mineral species can be the 
subjects of this process. To confound metamorphism with pseu- 
om is 
fore an error. It may be farther remarked, that, although certain 
pseudomorphic changes may take place in some mineral species, 
Thus this unproved theory of pseudomorphism, as taught by 
Bischof, does not, even if admitted to its fullest extent, advance 
us a single step towards a solution of the problem of the origin 
` of the various silicates, which, singly or intermingled, make up 
beds in the crystalline schists. Granting, for the sake of argu- 
ment, that serpentine results from the alteration of olivine or 
labradorite, and steatite or chlorite from hornblende, the origin of 
* Bull. Soc. Geol. de France, II, xviii, 678. 
+ Descriptive gue, Cry , p. 80, don Exhibition, 1862 ; 
also, Dublin Quar. Journal, July 1863, and Amer. Jour. Sci., I, xxxvi, 218. 
