422 BARNARD— ASTRONOMICAL PHOTOGRAPHY [April 20, 



with instruments that are extremely crude in comparison with the 

 elaborate and expensive telescopes with which our great observa- 

 tories are equipped today. Indeed in many cases the lenses were not 

 made for the purpose to which they have been put. It was only 

 incidentally that their services came to be of benefit to astronomy. 

 I have often thought of the strange difference in the present use 

 of these lenses and the one for which they were originally made. 

 Though it would be hardly fair to attribute their origin to the pur- 

 pose of human vanity, it was certainly vanity that had much to do 

 with it, for these large lenses were made purely for the taking of 

 portraits. In the days of the wet plate process the slowness of the 

 sensitive agent used in the plates made it necessary to employ very 

 large lenses so as to collect a greater quantity of light, and thus to 

 shorten the time of the sittings. Their use has therefore not fallen 

 to a lower level but has risen to a much higher one — from the 

 picturing of human vanity in the human face to the picturing of the 

 sublime features of the face of the heavens. Their great light 

 grasping power is no longer needed for the enlightenment of human 

 vanity — not that that evil has in any way become extinct — but from 

 the fact that with the extremely rapid dry plates of today the work 

 can be done with very much smaller and less expensive lenses. 



Description of Plates. 



NehulcB and Nebulosities. 

 For an example of nebular photography with a portrait lens 

 perhaps one of the best specimens is that of Plate I (exposure 4 

 hours), which shows the "North American Nebula." Though this 

 plate does not represent all that is visible on the original negative, 

 it yet shows how beautiful the nebula is, and how appropriate was 

 Dr. Max Wolf's naming of it. The nebula is not a faint object with 

 a telescope — indeed it was discovered over a hundred years ago by 

 Sir William Herschel. It is not, however, suited for visual obser- 

 vations. With a small telescope one sees only a diffusion of feeble 

 light which has no definite form or limits. It is, nevertheless, ex- 

 cellently and specially adapted for photographic representation be- 

 cause of the peculiarity of its light, which is very rich in photo- 



