VOL. LIII.3 i'HILOSOPHICAL TRANSACTIONS. 55 



the Royal observatory at Greenwich ; a determination very nearly agreeing with 

 that mentioned by Sir Isaac Newton, and which Mr. H. believes was deduced 

 from a comparison of Dr. Halley's and Mr. Cassini's observations. 



The Abbe de la Caille, in his memoir on the parallax of the moon, supposes 

 the difference of meridians to be Q"" 17% though he has not mentioned from what 

 authority he drew that conclusion. Mr. H. therefore supposes the difference of 

 meridians to be Q" 17'. — ^The last internal contact was observed at Paris by M. 

 de la Lande at 20^ 28'" 25' or 26' ; at 20*' 28"" 26' by Father Clouet, and by M. 

 Maraldi and M. Barros separately at 20'' 28™ 42'. Mr. Pingre, in a very curious 

 memoir on the sun's parallax already referred to, supposes the internal contact to 

 have happened at Paris at 20'' 28'" 38'. Mr. H. therefore makes use of the Abbe 

 de la Caille's observation at 20" 28"" 37'-i. 



The difference of meridians between Paris and Stockholm, says Mr. Wargen- 

 tin, is li" 2™ 51' or 52' at most. M. de la Lande, from a comparison of 17 ob- 

 servations of the first satellite of Jupiter, made from 17 50 to 1759, and commu- 

 nicated to him by Mr. Wargentin, determines the difference of longitude to be 

 jh 3m jQs. And the Abbe de la Caille, in his memoir on the moon's parallax, 

 supposes it to be l** 3"" 13'. As these last two determinations agree so nearly 

 together, Mr. H. supposes Stockholm to be l"* 3™ 10' to the east of Paris, and 

 Ih 12"^ 27' to the east of Greenwich ; and the last internal contact to have hap- 

 pened at 21'' 30"" 09' 5, which is a mean between the observations of Mess. War- 

 gentin and Klingenstiern. 



The city of Cajaneburg in Sweden is 38'" 40' to the east of Stockholm, ac- 

 cording to very late observations; and therefore Cajaneburg is Ih 51'"7' to the 

 east of Greenwich. The 2d internal contact happened at 22'" 7™ 59% when the 

 error in writing down the minutes is corrected according to the instruction given 

 inPhilos. Trans, for 1761. Indeed (supposing the longitude of Cajaneburg as 

 above set down to be exact) it is very easy to prove that the error of one minute 

 was made at the egress, rather than at the ingress. 



The city of Tobolski in Siberia (according to the observation of the end of the 

 solar eclipse on June 3d, by Mr. Chappe and Mr. Planmann at Cajaneburg, and 

 calculated by Mr. Pingre) is 2^ 42"* 1 1* to the east of Cajaneburg ; and this de- 

 termination is also confirmed by Mr. Wargentin's observation of the same phase. 

 Tobolski therefore is 4t> 33™ 1 8' to the east of Greenwich ; and Mr. H. supposes 

 Mr. Chappe to have observed the last internal contiict at 0" 49™ 23'-^-, without 

 making any allowance for the luminous ring which appeared round Venus in his 

 telescope. 



The observatory at Upsal (according to Mr. Wargentin in the Philos. Trans.,) 

 is l'' 1™ 10* to the east of Paris, and is therefore l'' 10™ 27* to the east of Green- 



