264 G. W. Cotles, Jr.— Distance of the Stars. 



(including his assistant, Dr. Schemer's) and those which are 

 not Voxel's ; the former class containing 48 and the latter 47 

 of the 95 stars used. The latter observations, besides being 

 widely variant among the different observers, have been shown 

 by Professor Yogel's measurements* to be nearly all too large; 

 which influences the result correspondingly. Vogel's measure- 

 ments have accordingly been invariably used, where possible, 

 to the exclusion of others; being estimated with approximate 

 accuracy to the tenth of a mile. Although compelled to halve 

 our already small number of stars, yet it may be worth while 

 to collect Dr. Yogel's observations (and the appropriate proper 

 motions) in the same manner as above, not only for purpose of 

 comparison, but with a probably much more accurate result. 

 This gives us 



2(a) = 10-994, 2(a) = 508-7 ; 



from which we obtain 



M(d) = 473,110,506,000,000 miles 



equivalent to 5,115,000 astronomical units, or about 80'5 light- 

 years, a little more than half the previous value. 



But it is to be noticed that these results, even if entirely free 

 from errors of observation, are only for the brightest stars 

 (since these alone give sufficient light for present spectroscopic 

 measurements), and hence for the nearest. But in any case 

 they can be only provisional, for several reasons, — first, as 

 previously stated, on account of the comparatively small 

 number of stars. Again, these stars, though distributed with 

 approximate uniformity, will be seen to be very scarce in 

 places occupied by the Milky Way, e. g. between the hours of 

 5 and 9, and 22 and 24, in right ascension. Again, as regards 

 their motions being at random, an examination of their direc- 

 tions (omitted for lack of space) will show that on one side of 

 the hemisphere the motion is almost entirely to the south, 

 while on the other side it tends toward the north ; and a 

 similar aggregation of signs will be noticed among the motions 

 in right ascension. •}-;{: 



* Following are Professor Yogel's observations in connection with his " List of 

 51 Stars," Monthly Notices R. A. Soc, June, 1892: " Greatest observed velocities, 

 + 302 mi. (a Tauri) ; — 24'0 mi. (y Leonis). Average velocity, 10*4 mi. No. of 

 stars with velocity greater than 10 - 4 mi., positive 7, negative 11. Average prob- 

 able error of the measurements for a single plate and one observer, ±l - 6 mi." 



f Similarly Professor Vogel notes of his observations, nearly all of which are in 

 the northern hemisphere (Monthly Notices, vol. lii, p. 96), that " fifteen of the 

 stars have a positive and thirty-two a negative motion" 



% This is due, I suppose, in part, at least, to the motion of the sun in its " way," 

 as the signs correspond pretty closely to what this motion would tend to make 

 them. It will be seen that when the stars are taken over a whole sphere, or a 

 hemisphere (as above), any general rectilinear drift, common in magnitude and 



