ape 
340 Prof, Beck on Lencous Action, as exhibited in New York. 
cut, to satisfy ourselves that these hydrous forms are by no means 
confined to one region or district, but seem at least in general to 
characterize the less ancient exhibitions of igneous action. 
If the question be now asked, whether the occurrence of these 
minerals, from which the water can be expelled by moderate 
degrees of heat, is not inconsistent with the idea that the whole 
rocks were ejected in a molten state, I refer the inquirer to the 
products of volcanoes. Nearly one hundred species of minerals 
are enumerated as occurring among the lavas of Vesuvius, anda 
considerable number of these are characterized by their containing 
water as one of their atomic constituents. I may here refer to 
Gehlenite, Davyne, mesotype, Comptonite, sulphate of ammonia, 
potash and soda—alum, &c. Nor need we be long in doubt asto 
the source of this water, when we see steam frequently ejected 
from voleanoes, and various compounds of hydrogen among theit 
products. 
_ [have thus noticed the difference in the effects of heat as ex 
hibited in the minerals found in the older rocks and in those of 
more modern eras, and have offered some suggestions in regard 
to the cause of this difference, drawn chiefly from the total ab- 
sence of water in the one class, and its frequent presence in the 
other. Let us now see what use can be made of the facts here 
brought forward, in determining the nature of those rocks which 
are commonly supposed to be the “ floor” upon which the strata 
are deposited. 
All geologists agree that the unstratified rocks “are generally 
of the nature of granite, that is to say, largely crystallized aggt@ 
gates of feldspar, with variable admixtures of mica and quartz,— 
or more rarely quartz and hornblende,—or- quartz and hyper 
sthene.” Granite is now considered, in whatever variety it may 
present itself, “as an older rock than any of the strata which 
rest upon it.” It is not, however, as was formerly supposed when 
granite was thought to be of aqueous origin, necessarily the Pr 
duct of an anterior epoch. There seems now to be no doubt, 
“that in very many cases the granite has been in a state of fusion 
since the deposition of several of the older formations, so that i 
has actually been injected into the fissures and cracks of thes? 
strata, or been raised up in a fluid mass among them.” In the 
language of Mr. Phillips, whom I have already quoted—* We 
may, therefore, consistently admit granite as well as other igneous 
