STELLAR PnOTOGRAPIIY. 



215 



226 



Plate 248. A second measure gave 7.0 instead of 6.2.(209. Spectrum uncertain ; 212 interferes. 



The mean value 6.6 has been adopted. The original 

 residuals were 351 1. Spectrum uncertain; 227 inter- 

 feres. 



141. Spectrum probably Type I, but not separated from 143. 



213. Spectrum uncertain ; 208 interferes. 



217. Spectrum uncertain; 227 interferes. 



447. Spectrum Type I, but the K line is visible, and about 0.2 

 as intense r,t the H line. 



235. 227 interferes. 



358. Plate 209. A second measure gave 7.0, but a more care- 

 ful estimate gave 7.5 instead of the original measure 8.0. 

 The mean value 7.5 has been adopted. The original resid- 

 uals were 4 2 51. Spectrum uncertain ; 349 interferes. 



208. Residuals in a, 11 ; in b, 10. 



120. Spectrum Type I. Presence of K line doubtful on ac- 

 count of interference of 115. 



192. Spectrum Type I, but too faint to <! ide whether the 



K line is present. 



280. Spectrum faint ; lines narrow, if present 



219. Spectrum uncertain ; 214 int turn. 



376. Residual in c, 10. 



101. Spectrum not seen ; 1 05 and 115 interfere. 



198. Spectrum not seen; 213 and 217 interfere. 



11. Spectrum faint. 



407. Residuals in a, 12; in l>, 14; in r, 15. 



109. 



103. 



204. 



all 



in b, 17 ; in c, 18. 



143. Spectrum probably Type I, but not separated from 141. 

 202. Spectrum not seen; 21 :> interfen 



seen 

 seen 



The spectra of Nos. 169 and 245 were seen, but 



faint 



type 



No trails were given by the 



26, 11, and 5 PleiaduMf which have the 



numbers 245, 169, and 107 in Wolfs Catalog 



An important inference may be drawn from the comparison of 



pectra of 



stars of this group. It is extremely improbable that chance alone 1 is brought 

 together so many bright stars in the same portion of the heavens. Most of them 

 probably have a common origin, and are much nearer to each other than to the 

 Solar System. A few, doubtless, have only an apparent connection with the group, 

 their real distance being much greater or less than that of the others. Ordinary 

 means foil to distinguish the individuals of these two classes. The similarity in 

 the chemical and physical conditions indicated by the apparent identity of most of 



the 



>pectra, is a strong confirmation of their common origin. 



© 



The variation in the 



spectra of such stars as Nos. 338 and 447 seems to indicate that these stars happen 



to lie in the same direction from us as the others, b 



are 



really connected 



with them. In a study of the parallax of the Pleiades, it seems very desirable that 

 these stars also should be observed. 



To determine the probable error of a single determination of bri 



o 



those 



stars only should be included which 



measured on 



four plates. The original 



uncorrected residuals are also used even in those cases where a second measure 

 showed that the first estimate was erroneous. The 140 residuals of the 35 stars 



included 



this 



give an average de 



of 



0.119 magnitud 



Using the 



ted residuals, the average deviation 



would be reduced to ±0.106. The prob- 



able error of a single estimate 



be 



119 X 0.976, or ±0.12, and the 



of 



o 



06. Of the residuals. 47 have the value 0; and 



pos 



d 



uals, 23, 15, 8, and 3 have the values +0.1, +0.2, +0.3, and +0.4, respectively 



Of 



