SECT. XXXVI. SHOOTING STARS. 423 



B Camelopardali, so that the earth's atmosphere comes into con- 

 tact with a zone of these small bodies twice in the year. By a 

 systematic series of observations, MM. Benzenberg and Brand 

 have clearly made out that the heights at which the falling stars 

 appear and vanish vary from 16 miles to 140, and their velocities 

 from 18 to 36 miles in a second, velocities so great as certainly to 

 indicate a planetary revolution round the sun. As shooting stars 

 are seen almost every night when the sky is 'clear, Sir John 

 Lubbock has thought it probable that some of these bodies may 

 have come so near, that the attraction of the earth has overcome 

 that of the sun, and caused them to revolve as satellites round it. 

 Should that be the case, they might shine by the reflected light 

 of the sun, and suddenly cease to be visible on entering the 

 earth's shadow. The splitting of the falling stars like a rocket, 

 and the trains of light, may be accounted for by supposing the 

 stars to graze the surface of the shadow before being eclipsed ; 

 and the disappearance would be more or less rapid according to 

 the breadth of the penumbra traversed. The calculations of M. 

 Petit, Director of the Observatory of Toulouse, not only render 

 probable the existence of small satellites, but tend to establish 

 the identity of 'a body revolving round the earth in three hours 

 and twenty minutes, at a distance of 5000 miles above its surface. 

 It is evident that in this case the same satellite would be seen 

 very often, and a very few would be sufficient to account for their 

 nightly appearance. It is possible, however, that some shooting 

 stars may belong to one class, and some to the other, since one 

 group may be revolving about the sun, and another round the 

 earth. In the case of a satellite shooting star, geometry furnishes 

 the means of ascertaining its exact distance from the spectator, or 

 from the centre of the earth, if the time and place of its disap- 

 pearance be known with regard to the neighbouring stars. Since 

 the falling stars are consumed in the atmosphere, their masses 

 must be small, but it is possible that occasionally one may be 

 large enough to arrive at the surface of the earth as an aerolite. 



