OF ARTS AND SCIENCES. 411 



method of searching for a luuar satellite. Photographs of the Moon, 

 taken at the Harvard station in Southern California, enlarging the 

 image in the telescope ; the results were compared with those obtained 

 elsewhere. Great spiral Nebula in Orion, invisible to the eye, but 

 covering a large part of that constellation. Method employed at Are- 

 quipa for making the 13-inch Boyden telescope follow the apparent 

 motion of a star. Instead of a finder, images in the photographic 

 telescope are used. The telescope is made to follow a star by means 

 of an eyepiece outside of the photographic field. The entire plate is 

 free to rotate around this eyepiece as an axis. The plate is then 

 turned at intervals so that another star is kept in the axis of a second 

 eyepiece. Sources of error, such as variations in flexure, in refrac- 

 tion, and in adjustment of the polar axis, which cannot be eliminated by 

 the ordinary method with a finder, are thus corrected. Photographs 

 of the clusters k Crucis, w Centauri, and 47 Tucana?. Chart and 

 spectrum plates of the vicinity of the variable star rj Carina?, showing 

 stars of the fifth type and other objects having peculiar spectra. Dis- 

 tribution of stars of the fifth type. Identity of the spectra of 

 a Aurigae and the Sun. Spectrum of (3 Auriga?, showing the lines 

 single and double. Spectrum of a new variable star in Scorpius, show- 

 ing the method of discovering variable stars of long period by means 

 of the bright hydrogen lines in their spectra. Charts showing this 

 star bright and faint. Light curve of this and of other variables. 

 Spectrum plates showing the presence and absence of the new star in 

 Norma. Charts showing the absence of this star before July, 1893, 

 and its presence since then. Identity of the spectra of Nova Norma? 

 and Nova Auriga?. Spectra of Nova Auriga? and o Ceti, showing 

 the difference between the spectra of new stars and variable stars of 

 long period. Method of detecting by inspection stars having a large 

 parallax, proper motion, or variation in light ; pairs of photographs 

 are taken at intervals of six months, with the film side of the plate out 

 aud in ; superposing plates taken six months apart in opposite posi- 

 tions so that the gelatine films are in contact, small deviations are 

 perceptible ; a motion corresponding to a parallax of 0".6 was thus 

 readily visible across the room. 



