1882.] from Wheal Newton. 24.' 



Again SCN= ft - NCA, 



and SCN 1 +SCN= 2tt - NCN V 



Hence <r=CN (sin NCA + sin NfiA) 



ory7vr . NCA + NCA NfiA - NCA 

 = 2CN sin 5 — l — cos — 1 <r— 



= 2CNsin | cos (? - <o - 6 - y + |j ; 



therefore e = - = 2 — sin vr sin ( <u — + 7 — 

 a a 2 \ 



Similarly 



„ Ar . a SCN-SCN 

 t = 2CATsin - cos _ * 



= 2CATsin | sin (ft - w-0 - 7+ | 



therefore ^r = t = 2 — p sin - sin (ft— to — # — 7 + ~). 



Now if the signals be at a considerable distance in comparison 

 with the radii of the circles, the differences ft — <u, ft — &>,, &> — 20, 

 g)j- 2</>, will all be infinitesimals ol the first order ; and w —0 may be 



replaced in the above formulae by — . The two angles e and yjr can 

 now be found. 



Again ^ = &> - m 1 , NAC=20-(o and A^ 0= &>. - 2<j> ; 

 therefore e = 2 (0 — (/>) 4- w 1 — (o. 



But 



e — yfr 



r/ = (o 1 — cf> — to — = co 1 — a) + — </> = — ~ — • 



Hence the value for the correction of the observed angle can 

 never exceed half the angle subtended by the positions of the edge 

 at either signal. 



May 29, 1882. 

 Professor Babington, Vice-President, in the chair. 



(1) Note on a table showing the time and place of the transit 

 of any star across the prime vertical circle in latitude 52° 12' 10". 

 By A. Freeman, M.A. 



Several problems of Practical Astronomy may be well solved by 

 the employment of a well-contrived altazimuth telescope so placed 



