428 BARNARD— ASTRONOMICAL PHOTOGRAPHY [April 20, 



eclipsed moon (exposure 9 minutes) in which the only illumination 

 is due to the sunlight refracted through the earth's atmosphere and 

 bent into the shadow of the earth onto the moon. One of the 

 reasons for making this picture was a hope that if any small body 

 should be attending the moon in its journey around the earth (a 

 small satellite for instance) it might be outside the shadow at the 

 time, and being thus illuminated by the sun, would show on the 

 photograph. The moon itself is ordinarily so bright that it would 

 drown out the light of any faint body that might attend it. 



Both the photographs of Plate VI are essentially ruined in the 

 reproduction. 



List of Lantern Slides. 

 This paper, when read, was illustrated by a number of lantern 

 slides of the various photographs. A list of these is given below for 

 completeness. I have arranged the slides in the order of subjects. 



L The Earth-lit and the Totally Eclipsed Moon. 



Slide /.—The new moon showing the lunar night, illuminated by 

 the " full earth." 



Slide ^.— This is the totally eclipsed moon illuminated only by 

 refracted sunlight coming through the dense atmosphere near the 

 earth's surface. 



IL The Milky Way, Star Clusters and Nebiilce. 



Slide 4. — The great star clouds of Sagittarius, east of the 

 Scorpion. 



Slide 5. — The double cluster of Perseus. 



Slide 6. — The nebulous region of Gamma Cygni. 



Slide /.—The " North American Nebula " in Cygnus. 



Slide (?.— The nebulous region of Rho Ophiuchi. 



Slide p. — The nebulosities of the Pleiades. This shows well the 

 remarkable thread-like strips of nebulosity, especially the one from 

 Electra and the one near and parallel to it. The extent of the nebu- 

 losities is greater than usually shown in photographs of the cluster. 

 The original negative shows the exterior nebulosities surrounding 

 the cluster. Exposure 3 hours 40 minutes. 



