398 Emmons on American Geology. 
rensselaerite, and octahedal iron ore,” besides what he calls pyro- 
5 aera sane as distinguished from laminated limestone, 
he however places in the laminated division of his pyro- 
aie whine with laminated serpentine, gneiss, mica slate, 
hornblende, talcose slate, etc., p. 43. He here objects to the name 
of metamorphic rocks as applied to gneiss, and the subsequently 
named rocks because ‘its use is theoretical, and was thus ap- 
plied on the hypothesis that those rocks are altered sediments, 
of which there is no evidence.” The italics are our own, 
shall let the author explain his notions of the origin of these pyro- 
crystalline rocks, which he tells us have been produced by the 
consolidation of the earth’s crust. 
** A pellicle must have ultimately been formed, and which still main- 
tains its existence as a constituent part of it. From the manner in whic 
the surface cools, the consolidated masses ihe successively form, 
must lie in contact with the inferior surface of the first-formed pellicle. 
The thickness of the crust increases from below 
So that the order which is observed in the hydroplasiic rocks 1 is in- 
verted, and “ the néwer are beneath and the older above 5. 
On the next page we are told that the first formed ce are the 
most highly crystalline, because the heat of the earth was great- 
est at the epoch of their formation, Weare at a loss to conceive 
what greater heat than that of a central fused mass can be re- 
quired, or what better condition for Bidet, by nase can be con- 
ceived than that of a mass slowly congealing between the outer 
crust and the central fire. We are then told that pce By are at 
first products gar tp from the cooling of the earth’s crust ; 
a consequence of the inverted orderSot succession alrea y e- 
scribed, it aeeid follow according to our author that granites 
in the next oe to class ps with granite asa pyro- 
een! rock, Further on, serpentine whose pyrocrystalline 
nature he has already asserted, is spoken of as an igneous rock, 
which, like other rocks of this class, has been formed at different 
veri Quartz pocks even when they have the character of 
1 ndstones, are set down as pyrocrystalline when found in the 
tale and mica bige while of clay slate, which is 
ed , line rock, bp Ar “Leip 
