-46 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1763. 



Greenwich. 



i7.il 



Aug 30 



Sept 13 



. 3 



4 



7 



+ 9 



Oct. 



'Mean of all 

 Meanrej.H- 



9.677 



9.324. 



9-096 

 10.161 

 1O.0O4 



9.515 

 io.y6i 



9.891 

 9-712 



Bologna. 



Paris. 



1751 



Aug.31 

 Sept. 1 

 13 

 14 

 Oct +7 



1751 



9.753 Sept.13 



9 895 



9.971 

 10.238 Oct 

 11.075 



14 



+ 24 



8 



10.186 

 9-96'i 



9-134 



9715 



11.912 



9895 



10.164 

 9581 



Stockholm. 



1751 



Sept. I 



25 



Oct +3 



6 



i 0.466 

 111.504 

 12.864 

 10085'Oct. 

 9.735 



UpsaJ. 



1751 



10.734 

 10.2(2 



Sept. 2 



+ 24 

 25 



61 



9.438 



12.2;.5 



9715 



9.13 



10.136 

 9.421 



Hernosand. 



1751 



Sept.25 

 27 



9933 

 lO.OU 



10.275 



By taking a mean of all these observations, it follows that the sun's mean 

 horizontal parallax is 10".2 ; and if we reject the observations which differ most 

 in excess from the rest, the mean will give 9.842 for the sun's mean horizontal 

 parallax. Besides these 27 determinations, the Abbe de la Caille compared 41 

 observations, the mean of which is given in the following table. 



N°ofObs. Observations. Instrunoents. 



7 The late M. Cassini and M. Maraldi Quadrant 2 f. rad. 



Mr. Deli.sle — at the Hotel de Clugny Mur, circle 2 f. 



Father Beraud Refr. tel. 7 f. 



M. M. Garipuy and d'Arquier Ditto 



M. Sabatelli and Father Carcani Quad. 4 f. diag. div. 



M. Bose Tel. of 6 and 8 f. 



6 

 3 

 6 

 12 

 7 



Places. O Par. 



Thuiy 8".982 



Paris t 11.532 



Lyons 9.020 



Toulouse 8.i;44 



Naples y.'s33 

 Wittemberg 10.<;9i; 



'ii. 



Mean of all observ. according to A. Caille 10.2 10 



Mean of Results (rejecting the 2d) 9.575 



« Few observations of Venus near the inferior conjunction with the sun on 

 Oct. 31, 1731, were made, on account of the unfavourable weather here in 

 Europe, By an observation made at Greenwich, on Oct. 25, the mean hori- 

 zontal parallax was Q".8 ; but according to the observation made at Paris on the 

 same day at the Royal Observatory, that parallax was 1 j*.4. On Oct. If, by 

 an observation made at Paris, the sun's mean horizontal parallax was Q'.SS ; but 

 by an observation at Bologna on the same day it was found to be 10".4. By the 

 observation at Paris on Nov. 17, the sun's mean parallax was 10".3. By a mean 

 of all the observations of Venus, the sun's mean parallax is 10 .38 ; and if we 

 rqect the Paris observation on Oct. 25, that parallax is 10.13.* We see then 

 that, according to these observations, the sun's mean horizontal parallax is not 

 less than 8".94. If we take a mean of the whole, that quantity is IO.O9 : but if 

 we reject the observations that differ most in excess, the sun's mean horizontal 

 parallax will be found to be 9''.92 ; a determination in which every astronomer 



• See the Abbe de la C.iiUe's Introduction to his Fphemerides Celestes from 1705 to 1774. 



