relations of the Metamorphic Rocks. 219 
morphism with pseudomorphism, as Bischoff, and others after 
im, have done, is therefore an error, It may be further re- 
marked, that, although certain pseudomorphic changes may occur 
in some mineral species, in veins, and near to the surface, the 
alteration of great masses of silicated rocks by such a process is 
s. 
fact that in many cases the intrusion of igneous rocks causes no 
apparent change in the adjacent unaltered sediments, shows that 
biares, with a temperature of 160° F., had, in the course of cen- 
> Si which, rising along certain lines of dislocation, and 
nee spreading laterally, might produce alteration in strata 
. * “Proc. Royal Soc. London,” May 7, 1857, and “Phil. Mag.” (4), xv, 68; also 
m. Jour. Science” ii, 487, and xxv, 435. 
(3, . Contpteg Beads be Peeoa” Nov. 16, 1857; also “ Bull. Soc. Geol. France,” 
1 XV, 103. 
