Section TII, 1888. 1 27 | Trans. "Roy. Soc. Canada. 



IV. — Tlie Lovr/i finir of tlir Toronto OJi-^rrrafori/. 



Ey CIhaklks CATiPMAEL, M.A., Director of the 01)servatory, and Prof. C. TLMcLeob, 



MoGill College^ Observatory, Montréal 



(Commnnioated M.ay 25tli, ISSS.) 



CONTENTS. 



Part T. By CnARLKS CARrjiARi,. — Intrndiietinn. In.strnnipnf s at Toronto. Redurt.ion of the Observations. 

 Part TI. By C. H. McLnoa— Tnstriinionfs at ?*Iont.roal. Star jilares. Oliservations and computation of Clock 



errors. Clock comparisons. 

 Part TII. By Charles Carpmaei,.— Observation.s and computation of clock errors. Personal er|n.ation. 



Clock com[)arisons. Comljination of results for detorminaMon of longitmle. 



PAE.T I. 



The loiio'itude of the transit instrument at the Magnetic ObserA'atory, Toronto, was 

 determined in 1840, by 18 sets of moon culminating stars giving a result of 5'' 1*1" 19' 

 west of G-reenwich, and also l)y a (Ximparison of chronometers with the Cambridge 

 Observatory. This latter determination gave for the longitude 5'' 11'" 3-3 . A mean 

 between these two determinations or 5'' 1*7'" 26' was employed as the longitude until 

 September, IBS'?, when a neAv value came into use, based on a determination in January, 

 185*7, made by Capt. Ashe, by exchange of signals by teli>graph lietwecn Toronto and 

 Quebec the longitude of Quebec having been determined by a similar interchange of 

 signals with the Observatory at Cambridge. No endeavour was made to eliminate the 

 effect of the personal equation of the observers. The determination gave 5^ 1*7,,, 33 .49, or 

 if we add .29, the correction to the longitude of Cambridge, as determined through the 

 Atlantic cable, we obtain for the corrected longitude 5'' 1*7 33'.*78. 



There being considerable doubt as to the accuracy of this determination, 1 arranged 

 with Prof. McLeod to cooperate with me in determining thi^ difference of lougitude 

 between the Toronto Observatory and the McGill College Observatory, soon after the 

 observations for the difference between that observatory and the Cambridge Observatory 

 had been taken. The method of work was similar to that described in the papex-, on the 

 longitude of McOill Observatory.' The only important point of difference -^^as in the 

 determination of the personal equation. In the determination between Cambridge and 

 Montreal the personal equation was obtained from observations taken at both stations ; 

 at each station a number of stars of all declinations were observed by both Prof Rogers 

 and Prof McLeod, one observer taking the star over the middle group of wires, and 



' Trans. Roy. Soc. Canada, 1885, vol. iii. sec. iii. p. 114. etc. 



