Astronomy. 



153 



At the end of the volume the results presented in it are col- 

 lated with those of the previous volume, thereby exhibiting the 

 results of all the work of the Winchester Observatory in parallax 

 from its establishment to the present time. 



The conclusions reached as to the relation of parallax to dis- 

 tance and proper motion appear in the following table : 



Proper Motion 



Mag. 



0-0-2-5 

 3-0-5-0 

 5-1-7-0 

 7-1-9-0 



0."00 to 0."34. 



+ 0-031 13 stars 

 + 0-026 9 ' 

 -0010 7 ' 

 ' 



0."41 to 0."54. 



+ 0100 2 stars 

 4 0-024 7 " 

 + 0-03414 " 

 + 0-040 23 " 



0."55 to 0."65. 



+ 0-113 3 stars 

 + 0-114 5 ' 

 + 0-06416 ' 

 + 0-032 23 ' 



i to 0."96. 



stars 



+ 0091 8 

 + 036 20 

 + 0-01819 



l."01 to 7."07. 



+ 0-200 2 stars 

 + 0-162 6 " 

 + 0-111 8 " 

 + 0-12812 " 



" While the groups are small there is, with slight exception, 

 manifest a very decided sequence of values both with respect to 

 magnitude and size of proper motion such as one might expect. 

 This is very gratifying in that it shows, in our opinion, as well 

 as does the comparison of different series upon the same stars, 

 that on the whole the work is comparatively free from systematic 

 error." w. b. 



2. Determination of the Solar Parallax from photographs of 

 JSros made with the Grossley Reflector of the Lick Observatory, 

 under direction of Charles D. Perrine. Pp. 98. Washington, 

 1910. Published by the Carnegie Institution. — The photographs 

 from which this parallax determination has been made were 

 taken at the opposition of Eros in 1900. Owing to the remote- 

 ness of the Lick Observatory from the others engaged in the 

 work, its measurements were arranged so as to admit of inde- 

 pendent reduction, and consisted of sets at large hour angles 

 east and west of the meridian, together with meridian observa- 

 tions of the planet for correction of the ephemeris. In the reduc- 

 tion most elaborate precautions have been used to detect all 

 systematic errors, with the result that everything except an insig- 

 nificant item of this sort has been satisfactorily accounted for. 



As a final check 20 of the plates showing the largest discrep- 

 ancies were remeasured and an independent determination of the 

 parallax made from them, and, almost as a work of supererogation, 

 even a third independent determination from the five most dis- 

 crepant of the former 20 plates was also carried through. 



The fact that neither of these determinations differs appre- 

 ciably from the full result is taken as a convincing test of the 

 absence of every source of appreciable error from measurements 

 and reductions. 



The correction deduced for the assumed parallax of 8'80* is 

 + ■0067" ±-0025". ' 



The probable error here given is estimated from the probable 

 errors derived in the following ways: 



