500 ADDRESS OF T. STERRY HUNT. 
announced my conclusion that serpentine, chlorite and steatite had 
been derived from silicates like sepiolite, directly formed in waters 
at the earth’s surface, and that the crystalline schists had resulted 
from the consolidation of previously formed sediments, partly 
chemical and partly mechanical in their origin. The latter being 
chiefly silico-aluminous, took, in part, the forms of gneiss and mica- 
schists, while from the more argillaceous strata, poorer in alkali, 
much of the aluminous silicate crystallized as andalusite, stauro- 
lite, cyanite and garnet. These views were reiterated in 1863,* 
and farther in 1864, in the following language, as regards the 
chemically-formed sediments: <« steatite, serpentine, pyroxene, 
hornblende, and in many cases, garnet, epidote and other silicated 
minerals are formed by a crystallization and molecular re-arrange- 
ment of silicates generated by chemical processes in waters at the 
earth’s surface.” Their alteration and crystallization was com- 
pared to that of the mechanically formed feldspathic, silicious and 
argillaceous sediments just mentioned. 
The direct formation of the erystalline schists from an aqueous 
magma is a notion which belongs to an early period in geological 
theory. Delabeche in 1834 conceived that they were thrown 
down as chemical deposits from the waters of the heated ocean, 
after its reaction on the crust of the cooling globe, and before the 
appearance of organic life. This view was revived by Daubrée in 
1860. Having sought to explain the alteration of paleozoic strata 
of mechanical origin, by the action of heated waters, he proc 
to discuss the origin of the still more ancient crystalline schists. 
The first precipitated waters, according to him, acting on the anhy- 
drous silicates of the earth’s crust, at a very elevated temperatire, 
and at a great pressure, which he estimated at two hundred and 
fifty atmospheres, formed a magma, from: which, as it cooled, were 
successively deposited the various strata of the crystalline schists.$ 
Chis hypothesis, violating, as it does, all the notions which soun 
theory teaches with regard to the chemistry of a cooling globe; 
has, moreover, to encounter graye geognostical difficulties. The 
