CHAPTER XXI. 



PHOTOGRAPHING THE STARS. 



WE have quite recently experienced one of the greatest 

 revolutions which the art of practical astronomy has ever 

 undergone. Professor Young, in an admirable article on 

 the subject, which has appeared in the Princeton Review, 

 has indeed regarded the impending metamorphosis as 

 parallel in importance to that which followed from the 

 invention of the telescope. Perhaps we should hardly 

 speak of the new departure as impending: we might 

 rather say that it nas already been in some degree realised. 

 We may fairly derive an illustration from the somewhat 

 similar change that our methods of illumination seem 

 likely to undergo. It will be generally admitted that the 

 present state of electric lighting is still in the initial and 

 tentative stages ; yet the overwhelming advantages of 

 electricity for many purposes is no longer disputed. Some- 

 what similar to the invasion of electricity on old-fashioned 

 sources of light is the invasion of photography into the 

 time-honoured methods of conducting astronomical ob- 

 servations. We cannot indeed assert that the application 

 of the photographic camera to the telescope is exactly 



