56 PHILOSOPHICAL TRANSACTIONS. [aNNO 1763. 



wich. By taking a mean of the 3 observations made there, the internal contact 

 happened at 21" 28'" 6'. 



Tornea° has been generally supposed to be l** 27™ 3(y to the east of Paris; 

 but with this difference of meridians, the observations at Tomea", though made 

 by Mr. Hellant, a very excellent observer, will give a parallax of the sun much 

 less than the other observations made in Jiigh northern latitudes. In order to 

 settle the longitude of this place, Mr. H. is of opinion that we may have recourse 

 with safety, and without incurring the charge of reasoning in a circle, to the 

 observation of the transit itself; viz. the observation of the internal contact at 

 the ingress. Whether we suppose the sun's parallax to be 8 ' or 10", the first in- 

 ternal contact would have happened sooner at Tornea° than at Stockholm 19' or 

 24'. As the sun's parallax will readily be allowed to be more than 8', Mr. H. 

 supposes the first internal contact to have happened 21' sooner. Tornea" is 

 therefore 24"" 55' to the east of Stockholm, and consequently 1^ 37™ 22' to 

 the east of Greenwich. Mr. H. makes use of Mr. Hellant's observation 

 of the internal contact, at 21*' 54"" 8', in preference to that of Mr. Lagerbom. 



Abo, the capital of Finland, where Mr. Justander observed the last internal 

 contact, at 21^ 45™ IQ' (when a correction is made in the minutes) is l*^ 11™ 29' 

 to the east of Paris, and l** 28™ 34' to the east of Greenwich. At Hernosand, 

 which is l'' 11™ 29' to the east of Greenwich, Mr. H. supposes the 2d internal 

 contact was observed at 21*^ 28™ 52', as published in the Philos. Trans, by Mr. 

 Short, from the Swedish acts. Mr. H. finds the island of Rodrigues, by com- 

 paring 3 observations of eclipses of Jupiter's satellites, with others made in Eng- 

 land and at the Cape, to be 4*' 12™ 38' to the east of Greenwich ; and this de- 

 termination is exactly confirmed by Mr. Pingre's comparison of the same eclipses. 

 The observation of the occultation of a fixed star gives the longitude 6' or 7* 

 greater. In the Philos. Trans., and even in the former part of the volume of 

 the Memoirs of the Academy of Sciences for 1761, we find the internal contact 

 was observed at Rodrigues at O*" 34™ 47'. And yet in the memoir on the sun's 

 parallax it is said to have happened ato"" 36™ 49'. On comparing this latter with 

 the time by the clock, it should seem that Mr. Pingre had committed a mistake 

 in subtracting the error of his clock instead of adding it. But he has no where 

 mentioned any reason for this difference. 



Gottingen, where the celebrated Mr. Mayer observed the first internal contact 

 at 20'' 58™ 26' to the east of Paris, is 30™ 16' or 39™ 33» to the east of Green- 

 wich. The Abbe de la Caille has placed Bologna 36™ 3' to the east of Paris. 

 By comparing the observations of the transit of Mercury, Mr. H. finds by a mean 

 of 3 results, agreeing very nearly together, that Bologna is 45"' 15' to the east of 

 Greenwich. Zanotti observed there the 2(1 internal contact at 2l'' 4™ 34'. But 

 as he used a refracting telescope of 2^ feet, and as two other observers with tele- 



