168 BULLETIN OF THE 



Remarks were made upon this paper by Messrs. Harkness, 

 Billings, and Woodward. 



At the conclusion of this discussion the Society adjourned. 



201st Meeting. May 28, 1881. 



The President in the Chair. 

 Thirty-four members present. 



The minutes of the last meeting were read and adopted. 

 The first communication was by Mr. D. P. Todd on 



THE SOLAR PARALLAX AS DERIVED FROM THE AMERICAN PHOTO- 

 GRAPHS OF THE TRANSIT OF VENUS, 1874, DECEMBER 8-9. 



In the volume of observations of the transit of Venus recently 

 issued, the photographs are presented in very nearly the form of 

 equations of conditions involving the corrections of the relative 

 right ascension and declination of the sun and Venus, and the cor- 

 rection of the adopted value of the solar parallax. The total 

 number of photographs is 213, of which 84 were obtained at stations 

 in the northern hemisphere, and 129 in the southern. 



Every photograph gives one equation of condition in distance, s, 

 of the form 



o = adA-\-66D + cdu — (o. — C.) 

 The normal equations in s are — 



-}- 23.99 dA+ 24.71 6 D — 28.72 Jw— 82.17=0 

 -J- 24.71 6 A -j- 184.66 <JD — 3.16 J u — 439.51 =0 

 — 28.72 6 A — 3.16 6 D -j- 484.51 d u -f- 21.72 = 



Their solution gives — 



<J A = 4- 1. "181 ± 0.^202 



d D = + 2. "225 db o. // 070 

 6 u = -f- o. // 0397 zh o/'c^iS 



Every photograph gives, likewise, one equation of condition in 

 position-angle, p, of the form 



o = a'6A + ydD + c'du — (o'. — C.) 



The normal equations in p are — 



-f 86821 17 J A — 1404261 (JD — 138999.20 c5w — 142109.4 = 



— 1404261 rf A -f 1521370 (ID — 25093.11 (lu -f- 10442.1=0 



— 138999.20 J A -|- 25093.11 6 D -f- 7326.76(50+ 2651.6 = 



