STELLAR PHOTOGRAPHY. 



221 



brightness in the Proceedings of the American Association, XXXIII. 8. Their desig- 

 nations, right ascensions and declinations for 1>80, and photometric magnitudes, are 

 estimated from that publication, and are given in the first, second, third, and 

 seventh columns of Table VII. The mean magnitudes of the photographic trails 

 are given in the fourth column, and the residuals in the fifth column. The sixth 

 column gives the magnitude corrected for declination, and the last column gives 

 the photometric minus the photographic magnitudes. Positive residuals indicate 



blue, and negative, red stars. The first four stars are a Ursce Minoris, & Ursa Minority 

 51 Ccphci, and X Ursce Minoris. The trail of the first of these is too intense to be 

 measured. 



A second reading of the trail of h, Plate 231, gave 9.3 instead of 8.8. The mean 



value 9.0 has been adopted. The original residuals were 2 1^. The red color of 

 \ Ursce Minoris is indicated by the large negative residual, the value of which is IS. 

 The readiest method of publishing the results obtained by any photographic 



process is to reproduce them so far as possible in paper prints obtained exclusively 

 by photographic means from the original negatives. In such prints, however, as i 



well known, many of the details of the negatives cannot be traced, and an unfavor- 

 able impression of the value of the work may thus be occasioned. On the other 

 hand, if every detail which may be detected in a negative is described, or repro- 

 duced by engraving, the original may be supposed to be far superior to other 

 photographs of nearly the same actual value. In the present case, no attempt at 

 an exhaustive studv of the negatives has yet been made. What is here described 

 may be seen upon them with little difficulty. 



Plate II. represents the central portion of photograph No. 6, taken on August 6, 

 1885, with an exposure of 72 minutes, and enlarged five times. It therefore repre- 

 sents the portion of the sky within about one degree of the pole. The scale is 

 five times that of the Durchmusterung, one degree equalling 10 cm. The stars 

 contained in the Durchmusterung zone -f 89° are here designated by their numbers 

 in that Catalogue. The designations of the other stars proposed as standards of 



— 



magnitude for faint polar stars, and given in Table VII., are also inserted. The trails 

 left by the stars are untouched, although, owing to the defects of the photolitho- 

 graphic process, they are very irregular. In the original they form perfectly smooth 

 lines. The Pole-star appears as a broad band in the left-hand lower corner. The 

 Voigtlander No. 4 lens, described on page 183, gave nearly as many stars as the 

 larger lens afterwards employed. DM. +89° 37, magnitude 10.5, was always well 

 shown, and under favorable circumstances star b, magnitude 12.4, was distinctly 



