148 
JOURNAL OF THE PLYMOUTH INSTITUTION. 
THE UNIVERSE. 
ABSTRACT OF MR. LANDON's PAPER. 
(Read November 23rd, 1876.) 
The lecturer explained that the motions of the heavenly bodies, 
subject to the law of mutual attractions, would be greatly modified 
if the bodies were assumed to move in a resisting medium, and 
that by these modified motions many perplexing astronomical ap- 
pearances could be explained ; e.g. the milky way, lines of stars, 
and the clustering together of stars in groups. 
Three causes of resistance were assigned : 
" (1) The atmospheres possessed by at least some of the heavenly 
bodies, though rapidly diminishing in density as the distance from 
the planet increases, would not entirely vanish, and would there- 
fore produce an infinitely small resistance on other heavenly bodies. 
" (2) Scientists generally admit the existence of ether in inter- 
planetary space, and hence probably throughout the universe. The 
resistance of this substance, though small, must be real. 
" (3) Our earth passes through more than one hundred streams 
of meteors, each stream containing many millions of bodies. These 
streams move in a direction opposite to that of the earth, and the 
actual impact of many with the earth forms a fully appreciable 
cause of retardation, especially when it is borne in mind that 
meteors weighing many tons have been found on the earth's 
surface. There is no reason to suppose that our planet meets more 
meteors than other planets, nor that the solar system possesses 
more than other stellar systems. 
" These retarding causes are placed in order of importance, the 
last being the most potential ; but in considering their effects, it 
is to be remembered that they are cumulative, and that infinitely 
small causes, acting during infinitely large portions of time, produce 
finite effects.' 1 
The lecturer then explained that the term " system of heavenly 
bodies" could be applied to comparatively small numbers of such 
bodies, where vast spaces, almost void, stretched between them and 
the rest of the universe, and that their relative motions could be 
calculated independently of such external bodies, though in con- 
sidering their absolute motions these external influences played an 
