COMETS AND AEROLITES. 



493 



ceeding so rapidly, and being just then 144,000 miles away, it escaped. 



We can scarcely estimate the results 

 of such a collision. This comet ap- 

 peared B.C. 34, and again at intervals 

 of about 575 years. It may be ex- 

 pected in 2255. It is to Halley that 

 the discovery of the elliptical orbits 

 of comets is due. 



M. Biela's comet was the cause 

 of much anxiety in 1832, for a colli- 

 sion with the earth was apprehended. 

 Fortunately a month intervened be- 

 tween the period at which the comet 

 was expected at a certain place in 

 the system and the earth's arrival at 

 that spot, so, as it happened, about 

 60,000,000 of miles intervened. We 

 cannot say what the exact effect of 

 such a collision would be, but some 

 wonderful atmospheric phenomena and 

 increased temperature would certainly 

 result from ^ , ^ 



the con- 

 tact. Now 



_- -til 



V IV 1 



Fig. 539 Path of Biela's Comet. 



the comet is supposed to have an effect upon 

 the vintage, as " comet " wines are regarded 

 with much favour. If comets, as is believed, 

 do consist partly of solid particles, a collision 

 might be unpleasant; but the weight is, as 

 rule, a mere nothing compared to their vapoury 

 volume, which is enormous. That the tails must 

 be of a very attenuated medium is evident, as 

 we can see the stars through them, and we know 

 that a very thin cloud will obscure a star. The 

 "menacing" comet, mentioned in the Spectator 

 February 1 88 1, will not do much damage, so the 

 scare was needless, as Mr. Proctor has explained. 



AEROLITES, or " Meteorites," are falling 

 bodies (meteors), which reach the earth in solid 

 form. The greater mass of falling stars are 

 burnt up ere they reach us, or are dissipated in 

 space. But many instances of aerolites descend- 

 ing might be adduced. They usually consist 

 of metals, such as iron and nickel mixed with sulphur, magnesia, 



*% 540 .-p a th of comet, 1680. 



