A HISTORY OF SCIENCE 



him all along the line of his observations, even, let alone 

 his inferences. But how one's egotism shrivels and 

 shrinks as one grasps the import of his sweeping 

 thoughts ! 



Continuing his observations of the innumerable nebu- 

 lae, Herschel is led presently to another curious specula- 

 tive inference. He notes that some star groups are 

 much more thickly clustered than others, and he is led 

 to infer that such varied clustering tells of varying 

 ages of the different nebulae. He thinks that at first 

 all space may have been evenly sprinkled with the 

 stars and that the grouping has resulted from the 

 action of gravitation. 



" That the Milky Way is a most extensive stratum of 

 stars of various sizes admits no longer of lasting doubt," 

 he declares, "and that our sun is actually one of the 

 heavenly bodies belonging to it is as evident. I have 

 now viewed and gauged this shining zone in almost 

 every direction and find it composed of stars whose 

 number . . . constantly increases and decreases in pro- 

 portion to its apparent brightness to the naked eye. 



" Let us suppose numberless stars of various sizes, 

 scattered over an indefinite portion of space in such 

 a manner as to be almost equally distributed through- 

 out the whole. The laws of attraction which no doubt 

 extend to the remotest regions of the fixed stars will 

 operate in such a manner as most probably to produce 

 the following effects: 



" In the first case, since we have supposed the stars 

 to be of various sizes, it will happen that a star, being 

 considerably larger than its neighboring ones, will at- 

 tract them more than they will be attracted by others 



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