DISTRIBUTION OF COMETS. 



261 



In strictness, the calculation should be made with refer 

 ence, not to the plane of the ecliptic, but to the plane of 

 the sun s equator ; and this might or might not render the 

 progression more regular. Probably, too, the progression 

 would be made somewhat different were the calculation 

 based, as it should be, not on the inclinations of orbit- 

 planes, but on the inclinations of major axes. But even as 

 it is, the result is sufficiently significant : since, though the 

 conclusion that comets are 11 5 times more abundant about 

 the poles of the ecliptic than about its plane, can be but a 

 rough approximation to the truth, yet no correction of it is 

 likely very much to change this strong contrast. 



What, then, is the meaning of this fact ? It has sev 

 eral meanings. It negatives the supposition, favoured by 

 Laplace among others, that comets are bodies that were 

 wandering in space, or have come from other systems ; for 

 the probabilities are infinity to one against the orbits of 

 such wandering bodies showing any definite relation to the 

 plane of the Solar System. For the like reason, it nega 

 tives the hypothesis of Lagrange, otherwise objectionable, 

 that comets have resulted from planetary catastrophes 

 analogous to that which is supposed to have produced the 

 asteroids. It clearly shows that, instead of comets being 

 accidental members of the Solar System, they are necessaiy 



