Resisting Medium. 247 
their condensat‘on ; unless, indeed, it be assumed that it has ever 
penetrated alike the interstices between the particles of solid, fluid 
and aeriform bodies; an assumption which might involve us in 
unauthorized conclusions. 
If this medium be possessed of gravity, as we might consist- 
ently presume, especially since it must otherwise tend to recede 
from the sun and planets into infinite space, leaving them and 
their satellites to revolve in vacuo; it may be considered asa 
circumsolar atmosphere, subject to the usual laws of atmospheric 
density and limitation, modified by its vast extent, its extreme 
tenuity, by any relevant peculiarities it may possess, and by the 
present and past condition and changes of the system. 
In objecting then to the prevalent opiion state! at the com- 
mencement of these remarks, it seems that we are authorized, by 
the state of such known facts, analogies and principles as relate 
to the subject, and by the condition and position of the argument, 
to presume that the resisting medium is finite in extent ; and that, 
ing so constituted as to obey the laws of physical ineshinnicl 
its particles, if once in a state of revolution about the sun, would 
ave a tendency to continue their motions, upon the same princi- 
ples according to which the planets describe their respective orbits. 
And therefore, whatever may have teen its primary condition, it 
must have, in the existing state of things, motions consentaneous 
with those of the sun and planets, which have been so long re- 
Volving in it, in the same angular direction, and in nearly the 
Same plane; since it could require a small fraction only of their 
Momenta, to communicate rotation to a medium so rare as to im- : 
pede very little bodies of immense magnitude, yet i 
ewting sensibly the satellites of Jupiter, when in elose prox- 
mity. 
Again, as the planets nearest the sun revolve most rapidly, the 
angular velocity of the ether must also vary with the distance. 
Supposing it to have ever been continuous, the exterior portions 
Would be accelerated by the friction of those near the centre, until 
the centrifugal force should exceed the centripetal, when the for- 
mer would begin to recede, thereby producing a successive sepa- 
tation into zones, upon principles somewhat analogous to those 
according to which, a similar arrangement of the primeval belts 
planetary vapors is alleged to have taken place. Whatever 
may have been its original condition, it would be difficult to con- 
