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AMERICAN GEOLOGY. 
illustrate, the subject under consideration. Notwithstanding 
this, it will be necessary to recapitulate certain facts and prin¬ 
ciples which have an intimate bearing upon the subject. 
In the first place, we must look upon all the repositories of 
the ores and metals as ancient arrangements, by which they 
are made accessible to us 3 and that those arrangements are the 
necessary result of the constitution of the globe. They are 
by no means to be regarded as accidents, arising from 
conditions which might have been otherwise. They, too, are 
general results, confined to no limited scale; and when the 
forces and plan were determined, upon which to form and 
fashion the earth, the results of which I have spoken became 
an essential part of those causes, and it would have, required 
special instrumentalities to have prevented their operation just 
as we now see them to have operated. It is for this reason 
that the formation of repositories for the metals has been con¬ 
trolled by law, by which certain constants may always be looked 
for. This being the case, the miner has not overlooked the 
plainest of these results, but is constantly referring to them in 
his operations with confidence. 
It is not necessary that we should connect these laws with 
the early conditions of the globe, in order to understand 
them; but as facts it is proper that they should be borne in 
mind. What was that original condition, then, which gave 
birth to the repositories of the metals'? It was that incandes¬ 
cent state of the crust of the globe, of which I have already had 
occasion to speak. We have no occasion now to inquire what 
gave birth to that incandescent state; the fact is attested in the 
phenomena everywhere visible in those portions of the earth’s crust 
which belong to its earliest epoch. The most important effect 
of this state is the expansion of the crust, or the occupation of 
a larger space for the time being. But the earth, situated in 
space, and in a colder medium than itself, has necessarily lost 
that primitive heat which belonged to its earliest stage of 
existence. It has cooled, and the most important result which 
interests mining, is the consequent contraction of the cooled 
