THE HISTORY OF A STAR. 69 



It is impossible with our present knowledge to suppose that at 

 any prior stage of the history of the heavens gravitation did not 

 exist. It is impossible, from what we know now, to suppose that 

 even the finest form of matter which entered our clearing in space 

 was not endowed with motion. Given this matter, its motion and 

 gravitation, let us next see what must very quickly follow. 



Gravitation will give us a formation of centers ; we shall get 

 a rotation (moment of momentum) due to the prior existence of 

 motion and to this formation of centers ; we shall eventually in 

 that way get condensing masses of this curdled substance. 



The moment we have these centers formed, gravitation again 

 will give us the motion of exterior particles toward these centers, 

 and the condensation in one part of space will necessarily be coun- 

 terbalanced by a clearing in another, so that, if we suppose that 

 the curdling was not uniform to begin with, the uniformity will 

 be less and less as time and this action go on. 



Let us imagine that here and there we have isolated eddies, 

 and here and there in the larger aggregations of the dust in the 

 most enormous swarms we can imagine we have also eddies ; 

 these eddies involved in the larger curdlings will be associated 

 with the phenomena of the general system of which they form an 

 insignificant part. These cosmical molecules aggregating in this 

 way will be, to compare great things with small, like the invisible 

 molecules of a gas. It is not too much to say, as Prof. George 

 Darwin has recently shown, that we shall have in effect the whole 

 mechanism of the kinetic theory of gases before us ; but, instead of 

 dealing with invisible gaseous particles, we shall have particles, 

 large or small, of meteoric dust. The kinetic theory tells us that 

 if we have encounters we must have a production of heat ; if we 

 have production of heat we must have the production of radia- 

 tion, although, if the heat be insufficient, the radiation may not 

 produce light enough to be visible to the human eye. 



It is a remarkable thought that all these changes to which I 

 have so far drawn attention may have been going on in different 

 parts of space for seons without any visible trace of the action 

 being possible to any kind of visual organs. I refer to this be- 

 cause it is right that I should point out here that Halley, who 

 was one of the first to discuss the possible luminosity of sparse 

 masses of matter in space, and Maupertuis, who followed him, 

 both laid great stress upon it.* When, then, these encounters, 

 which we may call collisions, take place, and when the heat due 



* " But not less wonderful are certain Luminous Spots or Patches, which discover them- 

 selves only by the Telescope, and appear to the naked Eye like small fixt Stars ; but in re- 

 ality are nothing else but the light coming from an extraordinary great space in the Ether ; 

 through which a lucid Medium is diffused, that shines with its own proper Lustre. This 

 seems fully to reconcile that Difficulty which some have moved against the Description Moses 



