MIRACLES OF SCIENCE 



telescope aimed with the utmost accuracy. This is 

 effected with the aid of a small direct-vision telescope 

 with two spider webs crossed in the field of vision. 

 The task of the observer is to keep a certain star just 

 at the juncture of the cobwebs. It is precisely the 

 same method by which a gunner aims the gigantic 

 cannon on a modern battleship. But the astrono- 

 mer's task must be kept up for hours together. 

 Moreover it is necessary occasionally to remove the 

 plate and refocus the instrument, to make allowance 

 for changes in temperature. 



The net result, however, in the hands of such an 

 expert as Professor Ritchie, is to produce, with the 

 five-foot reflector at Mt. Wilson, photographs show- 

 ing myriads of stars never hitherto revealed. It 

 shows also the presence of unpredicted nebulosities 

 in connection with certain stars. But, except for such 

 nebulosities, the brightest and faintest stars alike are 

 revealed only as points of light even by this most 

 powerful of telescopes. 



The chief value of the star photographs, as at 

 present studied, is not so much dependent on the 

 revelations of the myriads of fainter stars, as upon the 

 accurate charting of the positions of stars that are 

 nearer. Practically all recent additions to our knowl- 

 edge of the motions of the stars have been made 

 through study of the photographic plates. Indeed, 

 the modern astronomer is much more likely to be 

 found comparing photographic negatives in his labor- 

 atory than scanning the skies through a telescope. 



Doubtless the most interesting things revealed by 

 the modern observations of the stars relate to the. 



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