26 ASTRONOMICAL and 



And I shall conclude the paper by making those deductions 

 from them, which I hope, may in some measure, subserve the 

 interests of Astronomy. 



The elements for the calculations are from M. Mayer's 

 Tables of the Sun, published in the year 1770, and M. de la 

 Lande's Tables of Mercury, in the first volume of the second 

 edition of his Astronomy, published in the year 1771 ; 

 reckoning the difference of meridians between Cambridrre, 



and the Royal Observatory at Greenwich, 4*^ 44' 31"; and 

 between Cambridge, and the Royal Observatory at Paris, 



By these tables we find ^ 's distance from the Sun, reduc- 

 ed to the ecliptick, at the time of the conjunction. Log. 

 4. 498326, in numbers = 31501 ; the Sun's distance from the 

 earth. Log. 4. 995777, in numbers =: 99032 ; Mercury's dis- 

 tance from the earth therefore, in numbers, was 67531 — 



Log. 4. 829503. By the best calculations, from the observa- 

 tions of the transit of Venus, made in the year 1769 the 



of Mer 



Sun's horizontal parallax, on the day of the transit 



cury, must have been S'\ 85. Having these reanisite.^, we may 



find Mercury's horizontal parallax thus: ^'s distance 



from the earth : O's distance from it : : O's horizontal paral- 

 lax : ?^'s horizontal parallax; which is found =: 12". 978: 

 consequently, ^'s horizontal parallax from O = i\ 128. 



The Sun's horary motion, during the transit, was 



gi- 



2 30'; 7 : Mercury's heliocentrick horary motion in Ion 

 tude m the ecliptick, at the time of the first external contact, 

 was 14' 59"; and at the time of the second, 15-' r 

 quently, his motion from the Sun, 12' 28". 3 and 12' 32" 3 



conse- 



from 



