Dr. J. R. Mayer on Celestial Dynamics. 389 



space between celestial bodies contained no other matter than 

 that necessary for the existence of light (whether light be consi- 

 dered as emission of matter or the undulations of a universal 

 sether), this alone is sufficient to alter the motion of the planets 

 in the course of time and the arrangement of the whole system 

 itself; the fall of all the planets and the comets into the sun and 

 the destruction of the present state of the solar system must 

 be the final result of this action." 



A direct proof of the existence of such a resisting medium 

 has been furnished by the academician Encke. He found that 

 the comet named after him, which revolves round the sun in 

 the short space of 1207 days, shows a regular acceleration of its 

 motion, in consequence of which the time of each revolution is 

 shortened by about six hours. 



From the great density and magnitude of the planets, the 

 shortening of the diameters of their orbits proceeds, as might be 

 expected, very slowly, and is up to the present time inappre- 

 ciable. The smaller the cosmical masses are, on the contrary, 

 other circumstances remaining the same, the faster they move 

 towards the sun ; it may therefore happen that in a space of time 

 wherein the mean distance of the earth from the sun would 

 diminish one metre, a small asteroid would travel more than one 

 thousand miles towards the central body. 



As cosmical masses stream from all sides in immense numbers 

 towards the sun, it follows that they must become more and more 

 crowded together as they approach thereto. The conjecture at 

 once suggests itself tnat the zodiacal light, the nebulous light 

 of vast dimensions which surrounds the sun, owes its origin to 

 such closely-packed asteroids. However it may be, this much is 

 certain, that this phenomenon is caused by matter which moves 

 according to the same laws as the planets round the sun, and 

 it consequently follows that the whole mass which originates the 

 zodiacal light is continually approaching the sun and falling into 

 it. 



This light does not surround the sun uniformly on all sides ; 

 that is to say, it has not the form of a sphere, but that of a thin 

 convex lens, the greater diameter of which is in the plane of the 

 solar equator, and accordingly it has to an observer on our globe 

 a pyramidal form. Such lenticular distribution of the masses 

 in the universe is repeated in a remarkable manner in the dispo- 

 sition of the planets and the fixed stars. 



From the great number of cometary masses and asteroids and 

 the zodiacal light on the one hand, and the existence of a resisting 

 sether on the other, it necessarily follows that ponderable matter 



Phil. Mag. S. 4. Vol. 25. No. 169. May 1863. 2 D 



