POPULAR MISCELLANY. 



715 



Mediterranean slope. The laws of the dis- 

 tribution of rains, which M. Bclgrand an- 

 nounced in 1865 for the valley of the Seine, 

 are verified by the maps, and their general 

 application appears to be made more clear 

 every year. 



The Asteroids and Jupiter. Dr. J. IIo- 

 letschek has published, in the "Deutsche 

 Rundschau," a summary of our present 

 knowledge of the asteroids, or the group of 

 bodies which revolve in orbits between those 

 of Mars and Jupiter. Of the two hundred 

 planets of this group which had been discov 

 ered in July, 1879, sixty-three were discov 

 ered in the United States, sixty in France, 

 twenty-eight in Germany, seventeen in Aus 

 tria, fifteen in Great Britain, eleven in Italy, 

 five in Asia, and one in Denmark. Profess 

 or Peters, of the Clinton Observatory, has dis- 

 covered more (thirty-six) than any other sin- 

 gle observer. The orbits of one hundred and 

 seventeen were calculated in Germany, those 

 of forty-eight in the United States, and 

 those of the others in Austria, France, Eng- 

 land, Russia, and Sweden. The theory at 

 first adopted that these bodies are the frag- 

 ments resulting from the explosion of a 

 larger planet, was contradicted by the cal- 

 culations of Professor Newcomb, in 1860. 

 D'Arrest sought to establish the fact of a 

 connection among them by finding relations 

 in the eccentricities of their orbits, but the 

 elements of the planets discovered since 

 have set this theory at rest. The idea of a 

 collision of two bodies has also been given 

 up. The little planets mock all attempts to 

 combine their relations, and each asserts its 

 individuality as an independent member of 

 the solar system. They exhibit common fea- 

 tures only in the limitation of their orbits, so 

 far as the discovery of them has extended, 

 to a particular zone, and in a corresponding 

 limitation of their periods of revolution 

 around the sun. Taking the earth's mean 

 distance from the sun as unity, the halves of 

 the major axes of their orbits may all be 

 represented by numbers between two and 

 four. Their periods of revolution around 

 the sun are between four and eight times 

 that of the earth. Great variations occur 

 within these limits. Very perceptible and 

 peculiar intervals exist in several cases in 

 the mean distances of particular asteroids 



from the sun, which might once have been 

 accounted for by supposing that there were 

 planets not yet discovered which would oc- 

 cupy them. But as the numerous discov- 

 eries of new planets have failed to furnish 

 the bodies sought for, and have rather ren- 

 dered the gaps more obvious, it has been 

 suggested that the vacancies are not casual, 

 but are owing to a real natural cause. A 

 theory has been suggested that they are oc- 

 casioned by the attraction of Jupiter, and 

 is supported by the fact that a vacancy 

 exists at every distance from the sun at 

 which the time of a planetary revolution 

 would bear a definite relation to the year of 

 Jupiter. A planet could not continue in 

 such a position, for it would be subjected to 

 disturbances at every conjunction with Ju- 

 piter, the effect of which would be to draw 

 it out of its course and out of its relation 

 with the larger planet till it found a new 

 period of revolution not commensurable 

 with that of Jupiter. A large gap exists 

 between the asteroids Gerda and Sibylla, 

 in the place which a planet making two 

 revolutions to one of Jupiter would occupy. 

 Gerda, having an orbit interior to this 

 place, completes its revolutions in fifty-four 

 days less ; Sibylla, with an exterior orbit, 

 requires a period one hundred and two days 

 longer than that of half the year of Ju- 

 piter. Similar gaps exist at distances where 

 planets, if there were any there, would have 

 periods of revolution corresponding to two 

 thirds, two fifths, three fifths, two sevenths, 

 and three sevenths of that of Jupiter, al- 

 though planets are found on either side of 

 these spaces whose periods of revolution 

 bear no fractional relation, or an extremely 

 remote one, to that of Jupiter. Saturn also 

 produces modifications in the position of 

 the asteroids which are less noticeable on 

 account of its greater distance and lighter 

 mass. 



The Diffnsion and Softeuing of the Elec- 

 tric Light. M. L. Clemandot, a French en- 

 gineer, has invented a new arrangement for 

 the diffusion of the electric light, which, 

 he claims, presents considerable advantages 

 over the opaque globes hitherto employed 

 for that purpose. The globes operate by 

 absorbing the light until they become lumi- 

 nous a process in which a considerable pro- 



