BY J. J. DE FERRER. 227 



teen of egress observed in Europe, and comparing each of 

 these observations with the mean determination for Paris, it 

 appears that the greatest error in longitude has twice been at 

 8" of time. The errors of the mean of the observations of 

 the time of the ingress and egress, seems to be within 3", as 

 may be seen in the table. Air. Ellicott's observation appears 

 worthy of the utmost confidence and he says that the exte- 

 rior contact is within the limits of half a second. By the 

 European observations it will be seen, that the time employed 

 by the diameter of Mercury in the egress = 3' 02", 1 and ac- 

 cording to Mr. Ellicott's observations = 3' 05", 5 which proves 

 that both contacts were well observed: taking the mean, the un- 

 certainty appears to be 1" 7 and, all circumstances considered, 

 the error of longitude can scarcely equal 6" of time. 



From the new tables of Mr. Lalande. 



h l li 



Conjunction in the ecliptic. . . . . ". . . 1 04 36 



©'s true longitude from the mean equinox. . . . .46 54 17 3 



£ 's Helioncentric latitude. S. 5 47 470 



©'s aberration = — 19" 80 ; nutation = — 12" 6 



§ 's aberration in longitude. ^ -f. 6 85; aberration in latitude = — 3 28 

 ©'s horary motion. ......... 144 926 



© and ^ relative geocentric horary motion in the interval 7 na* nofi 



between the ingress and egress. $ 



§ 's horary motion in latitude. ....... 43 607 



© and § s relative horary motion between the ingress and 7 «» ofic 



the time of the conjunction. £ 



between the fgress and the conjunction. . . . 235 984 



$( 's horizontal parallax — ©'s horizontal parallax atthe time of the ingress 7 089 

 do. do. egress 7 109 



Equation of time at the ingress. ....... — 3 43 



do. egress. .. " , . . . . . — 3 44 2 



i diameter of the sun. . . . . . . . . . 15 51 8 



Observations made in Europe, May It It, 1799. Meantime 



Limb. Ingress of 3 Egress of $ 



h / m b 1 » 1 11 in 



Mr. deLambre. Paris. \ \ g jjJ'J j \ g j£ g 3 00 2 3 00 9 



Mr. Mcchain. Paris. | 2 21 19 52 V 4 41 19 0} • • • • 2 59 

 M ™ ■ -o ■ S 1 21 16 41 4 38 22 0} „ . n n «, no . 



Mr. Messier. Pans. i 2 21 19 51 4 41 30 C 3 10 ° 3 08 ° 



Island of Leon. I 

 Marseilles. 



1 4 03 58 3 



2 20 46 06 



1 4 50 26 



2 1 



G 



