J. D. Dana—Address of T. Sterry Hunt. 103 
ere ie * “The same causes that have originated the steatitic scapo- 
lites, occasional] picked out of the rocks, have given magnesia to whole 
rock-formations, and altered throughout their physical and chemical charac- 
ters. If it be true that the crystals of serpentine are pseudomorphous crys- 
ig altered from chrysolite, it is also true, as Breithaupt has suggested, that 
covering square leagues in extent, and common in most primary formations. 
The beds of steatite, the still more extensive talcose formations, contain 
everywhere evidence of the same agents.”—This Journ., xlviii, 92, . 
Besides this paragraph, expressive of my views, Mr. Hunt 
Cites also another of the same purport from my Mineralogy of 
oe and in this, also, I see little to modify. It is as follows: 
at— 
my simply of alteration of crystals, but in 7 ! 
ot rock. [Delesse admits this; see p. 99.) Th 
Mountain-masses, or the simple crystal, has been formed through a process of 
Pseudomorphism, or in more general language, of metamorphism ; the same is 
ed of other magnesian rocks, as steatitic, talcose or chloritic slates. Thus 
d € subject of metamorphism, as it bears on all crystalline rocks, and of pseu- 
a are but branches of one system of phenomena.”—WMin., 4th edit. 
b] a 
The larger part of the kinds of alteration or metamorphism 
made out against authors by Prof. Hunt, on pages 50, 51 of his 
article, are of this magnesian class, the results being serpentine, 
8 of caleite from gneiss or or or the reverse, until we so 
