Modern Igneous Rocks and the Primary Formations. 123 
explanation, that the heat was applied here through the waters 
heated by some eruption. As quartz is more soluble than feldspar, 
we may perhaps understand why we should find fused or round- 
ed quartz enveloping unaltered feldspar. 
Steatitic pseudomorphs of spinel, hornblende, pyroxene, &c. 
may perhaps be attributed to the same cause, that is, to heated 
magnesian waters, acting on spinels, &c. previously existing in 
the limestone. The steatitic spineis of Crange Co., N. Y.—which 
have a spinel skeleton, although mostly steatite—may have aris- 
en either from a large intermixture of steatite with the material 
’ of spinel while in the act of crystallization, or from an incomplete 
alteration of the spinel into steatite; I suspect the latter to be the 
true explanation. ‘The Rensselaerite of Prof. Emmons, appears © 
to be a steatitic pyroxene, as suggested by Beck, or rather a py- 
roxene changed nearly to a compact steatite. Its crystals, which 
are often distinct, have the form and angles of pyroxene, and leave 
little doubt that such was its origin, although it constitutes rock 
deposits of great extent in northern New York.* 
It is probably perceived that these views lead us to class the 
large family of taleose and chlorite rock, and steatite, among those 
that have been altered, like serpentine, by heated waters holding 
in solution magnesia, as well as silica. Excepting protogine, 
they are, in general, stratified rocks, and are classed by geologists 
in the metamorphic series. We do no violence therefore to ex- 
isting theories in supposing them to have been altered by heat ; 
and none we believe to reason or facts in supposing that this heat 
was administered in salt water. ‘The granitic structure of proto- 
gine as has been shown is no evidence that it is not metamorphic. 
In a protogine in Northern California, I observed distinct clayey 
fragments, appearing to have been derived from some compact 
feldspathic rock, which had undergone partial decomposition. 
The fragments could not be mistaken, and marked the rock as 
undoubtedly of fragmentary origin, although I was but half wil- 
ling to believe it at the time. The rock closely resembled gran- 
ite, yet was more disposed to crumble down. Protogines gener- 
ally undergo decomposition more readily than true granites. We 
find it difficult to account for this from their constitution, and 
may it not be owing to their metamorphic origin? 
* See Prof. Emmons’s Geological Report. 
