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times that of the poles. The studies of Pickering of Harvard 

 would reduce this to certainly not more than two times. The 

 discrepancy is due simply to the fact that the later counts go 

 further, the averages involve enormously greater numbers. The 

 inference is that if the investigation were carried very much 

 further if it were possible, to stars of the fifteenth magnitude 

 or beyond this difference of star crowding would quite dis- 

 appear. 



It will be seen, therefore, that as yet the problem is un- 

 solvable. It may be that the appearance of a grindstone stellar 

 aggregation is simply an illusion. It may, of course, always 

 be that it has no boundary, or, possessing a boundary, this 

 may lie for ever beyond our means of discovery. Before we 

 can form any idea of shape or of finitude, there is a fundamental 

 question which must be solved. This is the extinction or ab- 

 sorption of light. 



Our present theory of light was suggested and is to some 

 extent based upon the analogy of sound. We know that sound 

 is a wave process. In conceiving of light as of a similar nature, 

 the most, though not all, of the observed facts may be quite 

 satisfactorily accounted for. We know that the vibrations of 

 sound are progressively damped down by the medium in which 

 they are propagated in other words, that they eventually 

 wear out against the friction of the medium. The conception 

 of a light-carrying medium involves the idea that the ether is 

 to all intents frictionless. This is, of course, a philosophic 

 absurdity, if we conceive the ether to be of a material nature. 

 The inference, therefore, is that sooner or later the vibrations of 

 light would be extinguished by the medium through which they 

 travel. It may be, of course, that the whole ether theory will 

 later be discarded, and that there is no necessity for this con- 

 clusion. 



Be that as it may, we now know that space is nothing like 

 so empty as was formerly supposed. It is booming with suns 

 and probably a vastly greater number of dark bodies. If our 

 planetary system, with five or six hundred permanent members, 

 is an image or type of solar arrangements in general, the number 

 of planets, satellites, asteroids, and comets may be hundreds 

 or thousands of times the total number of central masses, 

 glowing or dark, just as the number of dark suns may be 

 hundreds or thousands of times those of the visible suns. 



