PHILOSOPHICAL TRANSACTIONS. 



181 



VOL. LXXVII.] 



This mean agrees pretty well with the observations on the 21st, 27th, and 31st 

 of August, whick are nearest the node, and most to be depended on. Aug. '2f, at 

 gh 12m q^Qs ^■^.^g |.jj^g ^(. Copenhagen, the heliocentric longitude of Saturn =9^ 21® 

 49' 27", and the distance from the node = 4l". Aug. 27, at 8^ 49™ 23% the he- 

 liocentric longitude = 9' 22° O' 12"; therefore, in 5"^ 23^ 36"^ 57^ Saturn has de- 

 scribed an arc of 10' 45^ and lO' 45" : 5^* 23^ 36"^ 57' = 41^' : ^. Hence Saturn 

 has spent 9^ 7"" 44* in going through those 4 1^'; and Saturn's passage through the 

 node happened August 21, 1784, at 18^ 20"^ 10% and the heliocentric longitude 

 of his descending node = 9' 21° 50' 8'^5. The errors in the place of the node 

 are relative to the tables of Dr. Halley +19' 39'% to the tables of M. Cassini + 

 16' 4% and to the tables of M. de la Lande + l' 31''% 



In the foregoing computation of Saturn's heliocentric longitude from the 

 tables of Dr. Halley, this longitude has been corrected for the perturbation after 

 the principles of M. Lambert. Though the geocentric places, calculated in this 

 manner, will agree still better with the observations than without those pertur- 

 bations, yet they are only empiric, and not founded on the theory and principles 

 of gravitation ; I shall therefore conclude this paper, by adding the faults in the 

 heliocentric places of Saturn, calculated only and directly from the tables of Dr. 

 Halley, which may be of some use to improve those valuable tables. 



Fill. Description of a Set of Halos and Parhelia, seen in the Year 177 iy in 

 North America. By Alex. Baxter, Esq. p. 44. 



Extract from a journal kept in the upper countries of North- America. At 

 Fort Gloucester, on the river of Lake Superior, six miles above the falls of St. 

 Mary's, and as much from the head of the river, where it issues from the Lake. 

 "January 22, 1771. Last night and to-day the frost has been more severe than 

 at any time this winter : I was hardly able, at mid-day, to keep my face to the 

 wind uncovered, though the sun shone very bright, and the sky clear. In the 

 morning the wind was easterly, which went about with the sun to the south and 



