496 ADDRESS OF T. STERRY HUNT. 
these anhydrous silicates, which are the subjects of the supposed 
change, is still unaccounted for. The explanation of this short- 
sightedness is not far to seek; as already remarked, Bischof, 
although a professed neptunist, starts from a plutonic basis. 
When the epigenic origin of serpentine and its related rocks was 
first taught, these were regarded as eruptive and unstratified, and 
it was easy to imagine intruded masses of dioritic and feldspathic 
rocks, which had become the subjects of alteration. As, however, 
the progress of careful investigation in the field has shown the 
stratified character of these serpentines, diallage-rocks, steatites, 
etc., and their intercalation among limestones, argillites, quartz- 
ites; gneisses, and mica-schists, and even among feldspathic and 
hornblendic strata, we are forced to reject, with Naumann, the 
notion of their epigenic derivation, and to regard them as original 
rocks, 
This view brings us face to face with the problem of metamor- 
phism as defined by me in 1860 * (ante, page 46). We must either 
admit that these crystalline schists were created as we find them, 
or suppose that they were once sands, clays, marls, etc. ; in 
a word, sediments of chemical and mechanical origin, which 
by a subsequent process have been consolidated and crystallized. 
Whence, then, come these silicates of magnesia, lime, and iron, 
which are the sources of serpentine, hornblende, steatite, chlorite, 
etc.? This is the question which I proposed in that same year, 
when, after discussing the results of my examinations of the ter- 
tiary rocks near Paris, containing layers of a hydrous silicate of 
magnesia related to tale in composition, among unaltered lime- 
stones and clays, I remarked that it is evident “ such silicates 
may be formed in basins at the earth’s surface, by reactions 
between magnesian solutions and dissolved silica ;” and, after 
some farther discussion, said “farther inquiries in this direc- 
tion may show to what extent certain rocks composed of calca- 
reous and magnesian silicates may be directly formed in the 
moist way.” + Subsequently, in a paper on “The Origin of 
some Magnesian and Aluminous Rocks,” printed in the ‘‘ Cana- 
dian Naturalist” for June, 1860, I repeated these considerations, 
referring to the well-known fey that silicates of — magnesia 
*Amer, Jour. Sci., II, x 135. 
t Ibid., IT, xxix, 23t; jay tT, xl, 49. 
t Ibid., II, xxxii 
a 
