
GEOLOGICAL HISTORY OF SERPENTINES. 199 
thus led to conclude that the ophiolites had been formed in the midst of the tertiary sedi- 
ments by contemporaneous sub-marine eruptions of magnesian and feldspathic magmas, 
and that the euphotides and other associated ophiolitic rocks had probably resulted from 
subsequent crystallogenic concentrations, which took place in these erupted magmas. 
Capacci, from his investigation of the ophiolitic mass of Monteferrato, in Prato, advanced a 
similar view, supplemented by the hypothesis of thermal waters accompanying the erup- 
tion of the magnesian magma or succeeding it. 
§ 92. Issel and Mazzuoli, from their joint studies in eastern Liguria, have formulated, 
more at length, an analogous hypothesis to explain alike the origin of the serpentines, and 
of the rocks there intimately associated with them, such as diorites, aphanites, variolites, 
and euphotides. To these, they give the general designation of amphimorphic rocks, sug- 
gested by the conception that they have had a two-fold origin, and have resulted from mix- 
tures and combinations of slowly deposited argillaceous materials of mechanical origin with 
elements brought in by abundant thermal springs through a long period, both during and 
after the eruption of the serpentinous magma. This latter, they suppose, was a phenomenon 
of short duration, almost instantaneous, while the formation of the euphotides and other 
amphimorphic rocks was a slow process. Nor is this the only effect ascribed to the hypothe- 
tical thermal springs, which our authors suppose to have acted upon pre-existing contiguous 
calcareous and argillaceous strata, penetrating them with waters holding in solution silica 
and oxyds of iron and manganese, and converting them to jaspers, phthanites or silicious 
slates, or to certain ill-defined silico-argillaceous or calcareous rocks which Issel has called 
hypophthanites. 
§ 93. The serpentines themselves having nothing in common with the argillites, sand- 
stones and limestones among which they are found, these observers have imagined that 
after the deposition of the eocene sandstone, great eruptions of a hot impalpable mud, 
consisting principally of silicates of magnesia and iron, generated by some unexplained pro- 
cess, were poured out from submarine fissures in the earth’s crust, were spread over the 
bottom of the sea, filling depressions therein, and were subsequently changed into 
serpentine. Thus, by this hypothesis, “the serpentines are considered as eruptive without 
being truly igneous, inasmuch as they do not contain in their composition any mineral 
which has been submitted to igneous fusion, and do not show, at their contact with the 
sediments adjoining, any metamorphic product due to a very elevated temperature. In 
order, however, to explain the slight traces of contact-metamorphism which are especially 
seen in enclosed masses of limestones, they admit that at the moment of its emission the 
magma may have had a temperature of several hundred degrees. As to the ophicalcites, 
which are often found at the contact of the serpentine with the sedimentary rocks, and 
sometimes even at a certain distance from these, their formation is attributed to the cement- 
ation of serpentine-breccias by calcareous waters discharged in the last phase ot the erup- 
tive period.” 
§ 94. Pellati sets forth, with wise caution, the preceding hypothesis as one suggested 
by the observers already named for the Apennine ophiolites, and adds that it might per- 
haps be also extended to the ophiolites of admitted eozoic age, which, he says, “ so far as we 
know at present, consist essentially of rocks of the same nature and the same composition.” 
He insists moreover upon farther researches, even in the case of the supposed eocene ser- 
