184 French National Injl'itute. 



tranfit announced for the 9th of November 1802, and hoped 

 he flioiild then be able to be convinced that his tables, one 

 of the mod important refults of his long labours, had reached 

 the utmofl: peifeftion to which they could attain in the pre- 

 fent ftate of the fcience. His wilhcs have been fully gratified 

 bv the obfervations we are about to detail. 



The moments of interior and exterior contact of the two 

 bodies ou the egrefs of Mercury were determined as follows : 



By 



C. Lalande takes as the mean terms of the two conta£ls 

 q''6'49", ando"8'j9'^ 

 From which he deduces the epefs of Mercury at 



o'> 7'" 34";' 

 The apparent diftance of the centres at that moment, 



16' 8-3''; 

 And the fame diftance reduced to the Cs;ntre of the earth, 

 16' lO'o'K 



Bv then comparing three differences of declination felefted 

 from twenty-five, which were meaiured by C. Meflier during 

 the tranfit, he deduces from them the fliorteft difiance of the 

 centres, namely 6^'^: and combining it with the diftance of 

 the centres at the moment of the egrefs, he is enabled to find 

 the diB'erence in longitude and latitude of the two bodies, and 

 the time elapfed between the middle of the tranfit and the 

 egrefs. We ihall not follow the detail of his procefs any 

 further, as our aftronomical readers may eafily fupply what is 

 here omitted; and to others it would be fuperfluous. We 

 only ftate the refults which C. Lalande obtained by this firft 

 method. 



He found the true conjunftion at 



9'' 2' 40''' mean time ; 

 The longitude, reckoned from the mean equinox for the 

 moment, 



r 16° 17' 9''i 



The geocentric latitude, 



53" North; 

 The heliocentric latitude, 



1' 54"; 

 The correAion of the tables : — 13" in longitude. 



C. Lalande 



