The Southern Heavens 41 



have been wrested from the darkness by the help of 

 photography. In fact the greater part of the work 

 which is being done to-day in the field of astronomical 

 research is being accomplished by means of specially 

 adapted photographic cameras. Photographic nega- 

 tives are more sensitive to the action of light than the 

 human retina, and the records which they furnish are 

 more correct, and are of course permanent. "The 

 personal equation' is to a certain extent eliminated 

 in photographic records. No two men see things 

 exactly in the same way; in fact, no two pairs of 

 eyes are exactly alike. The testimony given by as- 

 tronomers who have reported what they have seen, 

 when standing at the visual end of the telescope, is as 

 variant as the- testimony given by witnesses in law- 

 suits. The camera, on the other hand, if properly 

 adjusted and properly handled, gives sure results. 

 Astronomical research in these days has resolved itself 

 very largely into a quest for good photographic nega- 

 tives of the heavens. The popular conception of the 

 astronomer as sitting at the eye-piece of a great tele- 

 scope, sweeping the depths of space with eagle eye, is 

 reflected in the well-known lines of Keats: 



" Then felt I like some watcher of the skies, 

 When a new planet swims into his ken." 



''The watcher of the skies" nowadays is represented 

 by a small piece of glass, coated with a properly pre- 

 pared emulsion, upon which the distant heavens are 

 focussed, and which is exposed for minutes or hours at 

 a time to the starlight. The final result is a negative, 

 which presents the appearance of an assemblage of white 

 fly specks upon a dark ground. When one of these fly- 

 specks is discovered to have become a little elongated 



