VOL. 



LIII.] 



X 



PHILOSOPHICAL TRANSACTIONS. 



59 



made to agree by supposing an error of one minute in the observation at Rodri- 

 gues. has examined every source of error that might be committed ; and on the 

 whole sees reason to prefer his own observation to that of Mr. Mason, not be- 

 cause he could find no mistake in his own, but because he has proved that no 

 mistake could possibly be committed. His observation indeed is in some mea- 

 sure confirmed by comparing all the observations with that at Lisbon ; from 

 which comparison, if the longitude above laid down may be depended on, the sun's 

 parallax is somewhat more than 10 seconds. The several observations that have 

 been compared with the observations both of the Cape and Rodrigues, may also 

 be compared together ; and by combining some of them we may obtain different 

 results, on which we may more or less depend, as the differences between the 

 observed times are greater or less. 



PlaCi's compared. 



Diff". of Diff of 



Calculated observed 



times. ; time&. 



Tobolsk! and Greenwich 

 Tobolski and Paris. . . . 

 Tobolski and Gottingen 

 Tobolski and Stockholm 

 Tobolski ^nd Upsal. . . . 

 Tobolski and Bologna. . 

 Tobolski and Florence 

 Stockholm & Greenwich 

 Stockholm and Paris. . 

 Stockholm and Bologna 

 Stockholm and Florence 

 Tornea" and Gottingen 

 Tornea" and Paris .... 

 Tornea" and Greenwich 

 Cajaneburg &Greenwich 

 Cajaneburg and Paris. . 



Sun's 

 parallax 



9".734 



9.736 

 y.7i4 

 9663 

 9.64.6 



9.513 

 9.52.i 

 9.82+ 

 9-797 

 9.396 

 9-3+0 

 9-97* 

 9-91* 

 9.948 



10.054. 



10.003 



Places coinp^irt^i. 



Cajaneburg &Gottingen 

 Cajaneburg and Florence 

 Cajaneburg and Bologna 



Upsal and Paris 



Upsal and Greenwich. . 

 Hernosand and Paris . . 

 Hernosand & Greenwich 

 Hernosand and Bologna 

 Hernosand and Florence 



Abo and Paris 



Abo and Greenwich . . 

 Abo and Bologna .... 

 Abo and Florence . . . > 

 Tornea and Bologna. . 

 Tornea" and Florence. . 

 Greenwich and Paris. . 



Diff. of 



calculated 



times. 



°+7'..94 

 4+.5I 

 38.9;) 

 33.13 

 14.11 

 52.47 

 33.45 

 17.8f> 

 2338 

 42.46 

 23 44 

 7.85 

 13.37 

 45.64 

 51.16 

 19-02 



Diir. of 



obsTveH 



t imes . 



2"" 1' 



56 

 51 



4 1 

 21 



57.5 

 37 

 20 

 25 

 55.5 

 33 

 18 

 '2 23 



2 57 



3 2 



20.5 



The mean of the whole is 9". 695. 



Sun'j 

 parallax 



10". 08 8 

 9.628 

 9.679 

 9..SO8 

 9.836 

 9.402 

 y.3+2 

 9-139 

 9.101 



10.145 

 10.031 

 9.71 + 

 9-6i<^) 

 9.617 

 9.569 

 9.700 



It has been shewn that the parallax resulting from the total durations is 9".579 



— from a comparison of the observation at Madras with those of Tobolski and Cajaneburg is 9-763 



— from a comparison of the observed, with a calculated duration without parallax is 9-724 



— from the least distance of the centres 9-920 



— from the observations combined together ia 9.695 



It can hardly be supposed, as such different methods give a parallax of the sun 

 on the day of the transit equal to 9".736, that this parallax should yet be only 

 8".6q2, as deduced from a comparison of the observations with the Cape, while 

 the same observations compared with those of Rodrigues and Lisbon show that 

 the parallax exceeds 10 seconds. Let us therefore suppose that the observers at 

 the Cape have set down their observation one minute too soon, (though it must 

 be confessed that the time of the duration at the egress cannot warrant such a 



