656 



PHILOSOPHICAL TRANSACTIONS. 



[anno J 762. 



1 



Cajaneb. 



h. m. s. 

 5 58 1 

 8 5 



5 49 56 

 5 49 54 



— 2 



90 48 

 57" 



8". 53 



2 

 Calmar. 



h. m. ». 

 5 58 1 

 7 21 



5 50 40 

 5 50 39 



— 1 



0° 44^ 



52' 



8".52 



3 



Calcutta. 



h. m. s. 

 5 58 I 

 7 30 



h. m. s. 

 5 58 1 

 7 36 



5 50 31 

 5 50 36 



+ 5 



390 30* 



53" 



4 



Hernos. 



5 50 25 

 5 50 26 



+ 1 



40 4 



5 



Abo. 



h . m . s . 

 5 58 1 

 7 46 



5 50 15 

 5 50 9 



— 6 



50 43 



6 



Tobolsk. 



h. m. s. 

 5 58 1 

 9 3 



5 48 58 

 5 48 50 



Stockolni Stockoim 



.1. m. s. h. m. s. 

 5 58 1 '5 58 1 



7 34 



5 50 27 

 5 50 45 



54"! 55" 



8".40 I 8 '.48 [ 8". 61 



— 8 

 26° 50' 



64" 

 8". 63 



7 34 



5 50 27 

 5 50 42 



+ 18 

 30 24 



54" 

 8". 16 



Duration at the centre of the earth. 



Etfect of parallaxes from a parallax of 8.5 



Duration from a parallax of 8". 5 ofthesun 

 duration observed. 



+ 15 



30 24' 



54" 

 8". 22 



Ditf". of observation and a parallax ot8".5 



Altitude of the sun at ing'e's without refract. 



Alteration of duration by 1" of 0s parallax, 



Parallax of the sun from the observation. 



16 



Tranq. 



h. m. s. 

 5 58 1 

 6 24 



'duration at the centre of the earth. 



Effect of parallaxes, from a parallax of 8.5 



5 51 37 

 5 51 33 



— 4 



28° 44' 



45" 



Duration from a parallax of 8". 5 ofthesun 

 Duration observt.l. 



Diit". of observation and a parallax of 8". 5 



Altitude of the O at ingress without lefract. 



.^Iteration of duration by 1' of 0s' parallax. 



8". 67 I 8". 59 ! Parallax of the sun from the obs<rrv.iti< n. 



This table explains itself. If we therefore take the mean of the sun's parallax 

 arising from each of those l6 total durations, it will be found = 8''.48; and if 

 we reject the observations of number 7, 8, 9, 10, 12, 13, 14, which differ the 

 most from the rest, the mean of the 9 remaining ones gives the sun's parallax = 

 8^.55, agreeing to a surprizing exactness with that found by the observations of 

 the internal contact at the egress. 



The observations at Tobolsk and Cajaneburg I consider as very good ones, 

 the^e differing in the total duration only 6 seconds: this error in observation, 

 from what is gone before, may be very easily allowed. The observation of the 

 internal contact at the ingress at Stockholm is I believe too soon, and the uncer- 

 tainty of this observation may be easily granted, when it is considered thnt the 

 sun was only 3 or 4 degrees above the horizon at that time, and we find a dif- 

 ference of 22* between the observers at Upsal, where the sun was about the same 

 altitude. This I apprehend was owing to the undulation on the limb of the sun, 

 occasioned by the. vapours near the horizon: but the same reason cannot be 

 given for the observation at Tornea, where the sun was about 10° high, at the 

 time of the internal contact at the ingress, unless there was an undulation at that 

 altitude also, which may have been the case, though not mentioned. I have 



