44 Mr. H. A. Newton on certain recent 



For the weight of the individual ineteoroids he assumes one 

 gramme, relying upon the conclusions of Mr. A. S. Herschel, 

 who compared the light of the meteors with the light of a 

 candle, and hence inferred their weight. The estimate seems 

 too small ; for some of the trains fill cubic miles of space with 

 matter of sufficient consistency to form a cloud visible for 

 minutes (see Silliman's Journal, vol. xliii. p. 86). Yet the pro- 

 bable size of these bodies is so small that M. Schiaparellr's rea- 

 soning is still conclusive. 



To each sphere whose radius is fifty miles, he assigns, there- 

 fore, 1 gramme of matter. The cloud first supposed had only 

 1 the density of the resultant stream at the perihelion.. 



4000000 J ■ • n -iii 



Suppose, however, the space originally occupied by the meteo- 

 roids of the August stream to be only one million times that 

 now filled at the place where the earth traverses it. To each 

 gramme of matter would originally have belonged, in that case, 

 a volume equal to that of a sphere 10,000 miles in diameter. 



He then shows that a spherical group of bodies, each body 

 weighing 1 gramme, whatever be the dimensions of the group, 

 must have at a distance from the sun equal to the earth's mean 

 distance, a density such that the mutual distances of the mem- 

 bers shall be less than 1*86 metre (2 yards), in order that the 

 attraction of the sun may not dissolve the group. If the mu- 

 tual distances of the members exceed 1*86 metre, the sun acts to 

 separate the individuals from each other, not at the surface 

 simply, but throughout the whole extent of the system. 



But if the mutual distances are, as before determined, 100 

 miles, the dissolving power of the sun is 10 15 times the mutual 

 attraction of the particles. Inlike manner the dissolving-power 

 of the sun's attraction upon a group of similar bodies distant 

 20,000 miles from the sun, the mutual distance of the bodies being 

 10,000 miles, is 125,000,000 times the attraction which the 

 group has for one of its particles. This latter force then maybe 

 safely neglected. The dissolution or deformation of the system 

 must, moreover, begin much further away from the sun than the 

 assumed position of the cosmic cloud, out even in the stellar 

 spaces. It can enter the solar system only as a parabolic current. 



Even if we suppose a group that is tolerably dense approach- 

 ing the sun, as, for instance, a comet without a nucleus, there is 

 a certain limiting distance within which the differences of solar 

 attraction tend to dissolve it. If such a group passes this limit 

 in its descent to perihelion, the members will be scattered and 

 the original formation will never be restored. We have thus a 

 most singular effect of attractive force, namely, the dispersion of 

 a system that lacks coherence. 



If now a dense cloud of bodies is supposed to pass near one 



