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are physically unconscious of the presence of luminiferous 
ether, and this must be so if it approaches nearer to a 
simple subject of an enormous size, though if it be such a 
subject its conatus must be more potent than atmospheric 
air, and its constitution more simple. 
But neither the one nor the other nor both of them com- 
bined are the cause or the reason why they surround the 
earth everywhere. This cause under certain modifications 
may be said to originate in the earth herself. These modi- 
fications I now come to discuss. The earth, according to 
her density, I take to be the expression of the conatus there- 
of. And the fulness of her density is the fulness of her 
conatus. This conatus , like every other, acts within its 
subject for its production, maintenance, and manifestation. 
The subject, then, so far as the earth is considered, is the 
earth’s density taken as a whole. But if we say density is 
a subject we simply say that force is a subject, for where 
there is no force there is no density. But if density be the 
result of force then the density of a thing will be exactly 
proportional to the various forces within the various atoms 
of a subject to press themselves together. Hence, there will 
be as many kinds of density as there are forces or intensi- 
ties of conatus, and these will be manifest in their subjects 
whether simple or compound. But the more compounded the 
subject the more it is sensibly manifest or the more it is what 
is called substance. But just as the various elements of a tree 
are held together by an all-pervading conatus, so the totality 
of the conatus that are in the various elements of the earth 
are pervaded by a common conatus, and this common or 
universal conatus is manifest in the earth herself as the 
subject. This common or terrestrial conatus is exerted 
within and throughout the earth for her individual preser- 
vation as the subject of it. But if nature be uniform in her 
mode of operation this common terrestrial and earth pre- 
serving conatus must by means of its subject be able to 
