206 DR. THOMAS STERRY HUNT ON THE 
thesis just noticed, three others already mentioned, to which we must again refer. First 
of these, we have that which supposes the material of serpentine to have come from the 
earth’s interior as an igneous fused mass consisting essentially of olivine, which by sub- 
sequent hydration has been changed into serpentine. This strictly plutonic hypothesis 
being, however, by many geologists held to be incompatible with observed facts in the 
geognosy of serpentine, one which has been called hydroplutonic, and has already been 
set forth at length in these pages, has found advocates. These, conceding that the geog- 
nostical relations of serpentine require us to admit that it was laid down from water, have 
conjectured that a material so unlike that of ordinary aqueous sediments was ejected from 
the earth’s interior, not in a state of igneous fluidity, but as an aqueous magma or mud, 
consisting essentially of a hydrous silicate of magnesia, which subsequently consolidated 
into serpentine, and even into olivine and enstatite. This view, as we have seen, is main- 
tained by a school of Italian geologists, and Daubrée, while holding to the origin of ser- 
pentine by the hydration of a plutonic olivine-rock, supposes this to have passed into a 
hydrous condition before its ejection. * 
§ 115. There are, however, no facts in the history of vulcanism to justify this strange 
hypothesis of an erupted magnesian mud. The materials known to us as volcanic muds 
and ashes do not differ essentially, as regards their constituent chemical elements, from 
other detrital matters, and the origin of this conjecture may perhaps be traced to the 
unfounded assumption that olivine is peculiarly a plutonic mineral, and that rocks in 
which it and other magnesian silicates predominate are presumably plutonic in ,their 
origin. It isat best but a survival of the belief in a subterranean providence, which could 
send forth at pleasure from its reservoirs alike granite and basalt, olivine-rock and lime- 
stone, quartz-rock and magnetite. A rational science, however, seeks for the origin of 
these various and unlike mineral masses in the operation of natural causes, and endeavors 
to explain their production in accordance with known chemical and physical laws. 
Enlightened geologists are now agreed as to the aqueous origin of limestones, of dolo- 
mites, of iron-oxyds and of quartz, by processes which are intelligible to every chemist, 
and the formation in the humid way of the native silicates of magnesia is equally simple 
and intelligible. 
§ 114. It was, as already set forth in these pages, after a careful study of natural 
mineral-waters and sediments, and of the chemistry of artificial magnesian silicates, that the 
present writer, in 1860, ventured to assert the aqueous origin of the masses of native 
magnesian silicates, and their formation by reactions between the soluble silicates of lime 
and alkalies from decaying rocks and the magnesian salts of natural waters. f This 
view, although adopted by Delesse, as we have shown in § 11, and also, soon after by 
Gümbel, by Credner, and by Favre, has not found general recognition. I have, how- 
ever, to record the recent adhesion to it of Dieulefait, the eminent chemist and geologist 
of Marseilles, whose arduous and original studies have already placed him in the front 
rank of students in terrestrial chemistry; and also of Stapff, the learned and acute 
geologist of the St. Gothard tunnel. 

* Géologie Experimentale, p. 542. 
+ Hunt, Chem. and Geol. Essays, pp. 122, 296, 317. 
t Ibid. pp. 304, 305, 347. 

