37-J ANNUAL OF SCIENTIFIC DISCOVERY. 



same direction as other planetary bodies. These bodies, as a whole, 

 could scarcely change the eccentricity of the orbit of a planet, or 

 cause any sensible periodic inequality in the longitude. Their effect 

 upon the perihelion, however, might become considerable, since it is 

 the sum of the separate effects of each one ; so that the final result is 

 sensibly the same as if the whole amount of matter was concentrated 

 in a single mass. " Such," says Leverrier, " are the considerations 

 which have induced me to admit the existence of a ring of intra-Mer- 

 curial asteroids." 



Returning now to the consideration of the irregularities of Mars, 

 Leverrier finds that they can all be satisfactorily explained by sup- 

 posing, as in the case of Mercury, a ring of asteroids to exist within 

 the orbit of Mars, at a distance from the sun equal to the distance of 

 the earth from the sun, and having a total mass equal to a tenth of 

 that of the earth. This group of asteroids would accelerate the mo- 

 tion of the perihelion of Mars, just as an addition of a tenth to the 

 mass of the earth would do. If it is situated very nearly in the eclip- 

 tic, it will produce the same effect upon the orbit of Venus, and 

 therefore explain certain irregularities in the motion of the latter 

 planet. 



Finally, from the consideration of these and other data, Leverrier 

 announces that he has arrived at the following conclusions : 



1st. Besides the planets, Mercury, Venus, Earth, and Mars, there 

 exists between the sun and Mercury a ring of asteroids whose mass is 

 comparable with the mass of Mercury itself. 



2d. At the distance of the earth from the sun is found a second 

 ring of asteroids, whose mass is not greater than the tenth part of the 

 mass of the earth. 



3d. The total mass of the group of small planets situated between 

 Mars and Jupiter is not greater than the third part of the mass of the 

 earth. 



4th. The masses of the last two groups are complementary to each 

 other. Ten times the mass of the group situated at the distance of 

 the earth, plus three times the total mass of the small planets between 

 Mars and Jupiter, form a sum equal to the mass of the earth. 



The last conclusion depends upon the determination of the distance 

 of the earth from the sun by observations of the transits of Venus, a 

 determination which astronomers agree in considering as very accu- 

 rate. 



In regard to the hypothetical ring of planetary bodies encircling 

 the earth, M. Leverrier bases his opinion on purely astronomical 

 grounds, and he makes no allusion in his paper to a phenomenon 

 which will at once present itself forcibly to many minds, namely, the 

 aerolites falling from the atmosphere. For the last twenty years it 

 has been all but universally admitted that these falling masses were 

 of the nature of planetary bodies ; but there was nothing in the mode 

 or time of their occurrence to indicate that they had any connection 

 with one another, or with any known part of our solar system. They 

 seemed as independent, and to defy calculation or prediction as much, 

 as the non-periodical comets, without having the marks of brotherhood 

 which these display. Leverrier's discovery, therefore, comes oppor- 

 tunely to give us some idea of their origin. The aerolites, it may be 



