654 PHILOSOPHICAL TRANSACTIONS. [anNO 1 762. 



tact soonei than at the centre of the earth. The sum therefore of these two 

 quantities is = 7"" '9% by which quantity of time the observers at Greenwich 

 should have seen the internal contact sooner than the observers at the Cape in 

 absolute time, had the sun's parallax been = 8-I-'. But the difference in abso- 

 lute time as found by obsen'ation as above, is only = 7"" 15% therefore the sun's 

 parallax by supposition, viz. 8''.5, is to the parallax of the sun found by obser- 

 vation, as 7™ ig*" is to 7"^ 15% which gives 8 .42 (cr the sun's parallax, on the 

 day of the transit, by this observation, which numbers and result are set down in 

 number 1st, and so of all the rest in the table. By taking a mean of the results 

 of these 1 5 observations, the parallax of the sun, on the day of the transit, 

 comes out = 8^47, and by rejecting th^ 2d, the 8th, the 12th, and 14th results, 

 which differ the most from the rest, the sun's parallax, on the day of the transit, 

 by the mean of the 11 remaining ones, is = 8".52. 



We have received from Sweden several obser- 

 vations of the total duration of the transit from ^aja»eburg = 9s. 50 



. . Calmar = y O 



the internal contact at the mgress, to the inter- Calcutta = 9 50 



nal contact at the egress, and also the observa- ^^"^^^^^ ~ ^ ^? 



tion of the same duration by M. Cliappe at To- Stockholm ..........= \\ 0— 



bolsk in Siberia, and by several persons in the ^tockholm = 10 75 — 



East Indies; but the differences between these Upsal .......... ....^ 6 70 



durations are too small to determine with any Upsal = 9 



, , 11 /> ^i 1 Tornea = 12 0— 



accuracy, the sun s parallax trom them, by com- Xomea = u 0— 



paring the duration at one place with the dura- Madras = () 70 



tion at another. The greatest difference be- xranquebar ..........= s 75 



tween them, and the duration at Tobolsk, which The mean of these 15 results gives 

 is the least, amounting only to 2- 5(y, and the t! r:]^: F7^:^fi^I 

 least difference amounting only to 1"^4^: in most from the rest, the mean, of the 

 which small quantities the unavoidable errors of Z7'M9^ ' '' ^"'^' '^^ '""' ^"■'"''' 

 observations must be^r a considerable propor- 

 tion, and yet by comparing 15 total durations observed at different places with 

 the total duration observed at Tobolsk, I find the annexed results of the sun*s 

 parallax from each of them. 



However, on calculation by another method, I find so great an agreement 

 between thein, on the supposition that the sun's parallax is = 8^% that I have 

 determined the sun's parallax from them also, as a corroboration of the sun's pa- 

 rallax being very nearly the same as found by the observations of the internal 

 contact ; and this is done in such a manner that each observation of the total 

 duration at any one place, determines the sun's parallax independent of any ob- 

 servation of the same duration made at any other place, and in which an exact 

 knowledge of the longitude, of the latitude, and of the time at the place of ob- 



