PRITCIIARD S WEDGE PHOTOMETER. 



30.3 



chart of the region following y Pegasi. They are designated by corresponding 

 numbers in Fig. 1. On the original chart their magnitudes were given as follows, 

 viz.: No. 1, 10th; No. 2, 11th; No. 3, 11th; No. 4, 11th; No. 5, 11th; and No. 6, 

 13th. Of course these magnitudes, shown by the symbols on the chart, are only 

 intended to be roughly accurate, no gradations smaller than whole magnitudes 

 being indicated. The points surrounded by dotted circles indicate stars not con- 

 tained in the original chart, but added by the Princeton telescope. The observa- 



Region following j' Pegasi. Photometer Stars. Octorek, November, 1886. 



S. 5-' 



N.5' 



2" 20" 



2" 40" 



Scale of magnitudes 



in 

 * 



11 

 * 



12 



+ 



13 14 



3" 20- 



Fig. 1. 



tions were made in the following order. First, five extinctions of Nos. 1, 2, 

 and 3, then five each of 3, 2, and 1, in reverse order; the whole thirty ex- 

 tinctions taking about an hour and a quarter. Then five extinctions each were 

 made of the smaller stars, 4, 5, and 6. On the first night, however, only No. 5 

 was observed. 



In reducing the observations, the mean of the thirty readings of the first three 

 stars was taken, and the mean of all the readings of each of the stars was compared 

 with this mean. In the table below. A,, Aj, etc. are the differences between the 

 extinction points for each star and the mean of Nos. 1, 2, and 3 ; the columns headed 

 r are the differences between the individual results and the mean result for the 

 four evenings. A plus sign in the A column denotes that the star was brigJder than 



