246 JResistinsf Medium. 



Art. III. — Remarks upon some of the probable effects of a Resist- 

 ing Medium ; by Thomas H. Perry, Prof. Maths. U. S. N. 



It is a somewhat common opinion, that the resisting medium 

 believed to occupy the planetary spaces, must eventually destroy 

 the motions of the solar system. This conclusion does not seem 

 to me to be justified by the state of the facts at present known : 

 and, although it may not be easy to demonstrate the absolute im- 

 possibility of such an effect, the admirable provisions for the con- 

 tinuance of the present arrangement of the heavenly bodies, 

 which science has already elicited, ought to be considered, at 

 least until contrary probabilities are shown to exist, presumptive 

 indications of its future permanence. 



The final effects of a resisting medium must depend upon its 

 extent and mode of distribution. The facts from which its exist- 

 ence is deduced, do not apprise us whether it is, or is not, limited 

 to a comparatively small distance from the sun : nor whether it is 

 diffused continuously from this luminary to the remotest limits of 

 his system, or is disposed about him in concentric zones, separated 

 by intermediate spaces, incapable of impeding ponderable bodies. 

 It is not a legitimate ii]ference that the medium by which comets 

 are retarded is essential to the transmission of light, and therefore 

 the visibility of the remotest stars, which would in that case be a 

 relevant fact, has no necessary connection with the subject. 



Were it proved that the ether is in its extent as unlimited as 

 space, and that its elasticity is no where counterbalanced by any 

 kind of attraction, it would indeed follow that its effects, how- 

 ever inappreciable and indefinitely slight in any firrite period, 

 must become sensible, when augmented by the increments of 

 time in the same degree indefinitely great ; and that the planets, 

 as has been often asserted, must, in the lapse of a sufficient series 

 of ages, fall to the sun. 



But while we have, in known facts, no evidence that the ether 

 is thus universally diffused, we are led by analogy and the favor- 

 ite theories of the age, to presume the contrary. If, as every cir- 

 cumstance that has any bearing upon the subject conspires to 

 evince, all the ponderous globes in the universe, once pervaded 

 space as attenuated nebulae, surely it must require great elasticity 

 and expansion of the ethereal matter to fill the vacuum formed by 



