Resisting Medium. 249 
ist. The circumferences of circles being as their radii, and 
gravity inversely as the square of the distance; the centrifugal 
force of portions remote from the primary, at length exceeding 
the force of attraction, must cause them to recede; and this pro~ 
cess must continue as long as the momenta of the planet and its 
satellite continue to be transmitted to the circumference of its 
tenuous atmosphere. 
2nd. 'The rotation of any mass having motions similar to those 
of the planets, must, as might easily be proved, have a tendency 
to remove a resisting medium from its path, and therefore if ever 
the ether were so disposed as to interfere with the motions of the 
planets and their satellites, it must, unless retained by causes of 
whose existence we are not apprised, recede from the emai of 
their orbits. 
3rd. So much of the ether as should nevertheless be retained 
by the attraction of any of these bodies, would probably be dis- 
posed in concentric zones, analogous to those in the general sys- 
tem, and upon similar grinciples after the separation of which 
zones, the influence of a resisting medium would cease to be felt, 
at least until their arrangement should be disturbed. 
4th. And finally, as the magnitude of the planetary bodies was 
probably much greater formerly than at present, it may be pre- 
sumed that most of these changes occurred before the process of 
condensation was completed. 
The ether once distributed throughout the system as has been 
indicated, and with the elements of readjustment, must resist the 
action of a disturbing force. A cause of disturbance exists in the 
excentric motions of comets, which in their course must n 
rily displace portions of the intersected zones. But this cause can 
hardly exceed the force requisite to render their present orbits 
consentaneous with the general motions of the system. Besides, 
while it acts with exceeding slowness in widely distant regions, 
it operates at the two intersections of each zone made in a revo- 
lution, in nearly opposite directions ; and therefore comparatively 
feeble as the resulting forces must be, under any circumstances, 
it is possible that in consequence of its mode of operation, this 
cause may effect little else than temporary oscillations of the me- 
dium until it ceases to act. 
The consideration of influences and consequences foreign to 
the system, has been thus far, for the most part, purposely avoided. 
Vol. xxxvi, No. 2.—Jan.—March, 1840. 32 
