46 Mr. II. A. Newton on certain recent 



" V. The number of meteoric currents crossing the spaces of the 

 solar system at all possible distances and in all directions is probably- 

 very great. The exceeding rarity of the matter contained in them 

 allows these currents to intersect mutually without causing any dis- 

 turbance to one another. They may undergo progressive transpo- 

 sitions and deformations in space, like rivers which slowly change 

 their bed. They may be interrupted, and thence become double or 

 multiple, and they may even in particular circumstances become 

 closed elliptical rings. The November meteoroids are apparently 

 portions of such a ring in process of formation. 



"VI. The cosmical clouds having short periods of revolution 

 around the sun, by which some are inclined to explain the appear- 

 ance of shooting-stars, cannot have a permanent existence without 

 violating the known laws of universal gravitation. 



" VII. The matter of the parabolic currents, after having passed 

 the perihelion, returns into space in a state of dispersion greater than 

 that which it had before the passage. In particular cases, as when 

 the current meets a planet, very great perturbations may ensue, and 

 a separation of some of the meteoric stars into special orbits. Such 

 stars from that moment may be called truly sporadic. 



" VIII. Thus the meteoric stars, and other celestial products of 

 analogous nature, which in past ages were commonly regarded as 

 atmospheric phenomena, which Olbers and Laplace first ventured to 

 make to come from the moon, and which at a later period were raised 

 to the dignity of members of the planetary system, truly belong to 

 the category of the fixed stars ; and the name falling stars expresses 

 simply and precisely the truth respecting them. These bodies have 

 the same relation to comets that the small planets between Mars and 

 Jupiter have to the larger planets. The smallness of the mass is in 

 each case compensated by the very great number. 



" IX. Since we may safely regard it as certain that falling stars, 

 bolides, and aerolites differ in nothing except their magnitude, we 

 may conclude that the matter which has fallen from the sky is a 

 fragment of that of which the stellar universe is formed. And as in 

 such matter there is no chemical element that is not found upon the 

 earth, the similarity of composition of all the visible bodies in the uni- 

 verse, already rendered probable by researches with the spectroscope, 

 acquires a new argument for its credibility." 



The further question is then broached whether it is necessary 

 for the original cloud to be made up of such small elements ; 

 whether, for example, it may not consist of a moderate number 

 of comets. In such a case, we ought to meet from time to time 

 with orbits somewhat unlike, which intersect each other in the 

 depths of space, but which lose the characteristics of a common 

 system, owing to considerable intervals between the times of 

 perihelion passage. 



The question is not a new one. Prof. Hoek of Utrecht has 

 found several double and triple systems of comets *, which at a 

 * Monthly Notices, vol. xxv. p. 243; and vol. xxvi, pp. 1 Si 204. 



