GEOGNOSY AND GEOLOGY. 139 
definite and regular order of succession, in which we may always distinguish 
one superimposed or applied stratum or series from another subjacent to it. 
Normal masses consist partly of isonomic, partly of heteronomic rocks; the 
former generally prevailing in the older, the latter in the newer formations. 
A somewhat similar relation exists in the isonomic rocks in which silex or 
carbonate of lime prevails; the former is generally inferior, the latter 
superior. In most strata of rocks there is not the least difficulty in determining 
that they have been deposited from water, especially from sea water ; such 
rocks are called Neptunian. In others, again, this aqueous character is 
obliterated to a greater or less extent, and for certain reasons we conclude 
that such have been transformed from their original condition to their 
present by means of various agencies; such are called metamorphic 
rocks. 
The occurrence of fossil remains is as characteristic of the normal masses 
as their absence is of the abnormal. They are found in very many of the 
normal rocks, but following them up from the recent formations to the more 
ancient, we after a time find that they cease to present themselves. The 
class of normal deposits falls naturally into three orders, as established by 
Hausmann: into bottom series, middle series, and top series. Others, as Elie 
de Beaumont, Sedgewick, Murchison, and others, do not receive this 
arrangement, not separating the bottom rocks so decidedly from the others, 
but including them with the transition; the basis of their division would 
rather be into palzozoic, secondary, and tertiary. 
Bottom SeErtzs. 
The principal character of these rocks consists in their forming the basis 
upon or against which all the other normal masses rest. They occur as 
well at great depths as at considerable elevations, either free or covered by 
other rocks. Their purely chemical formation is unmistakable, for the 
species composing them are all of crystalline texture; and this character is 
so universal as to enable us confidently to assert the absence of the 
bottom series where conglomerates exist. Silicic acid is one of the most 
predominating ingredients, both in the form of a silicate and of silex. It is 
combined generally with the oxydes of aluminium, potassium, sodium, 
calcium, magnesium, iron, and manganese, with them forming micaceous 
and feldspathic minerals. That the rocks of this division are metamorphic 
is exceedingly probable ; at least we know this to be the case with respect 
to crystalline limestone, or marble, this occurring in fact as a subordinate 
mass between the crystalline shales. It must be remembered that the 
bottom series were most exposed to the influence of the abnormal masses, 
from resting immediately on them. The frequent eruptions from the 
heated nucleus of the earth, formerly of much greater extent than at present, 
appear to have attacked these strata first, filled them with cracks and 
fissures, and metamorphosed them by the influence of a high temperature. 
It is also exceedingly possible that the ascending central heat of the earth, 
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