The Great Comet of 1861. 259 
stars themselves. Many such have appeared within the ] 
Aoaig years. Suppose such a comet bag © suitably placed es 
a e observed simultaneously in different quarters of the globe, 
Mose ata distance from the earth of less than one-twentieth of 
“one un’s distance. Under favorable circumstances it would not 
; azarding too much to say, that in the course of its apparition 
; eps error of the solar parallax could be reduced within 
taller limits than is possible by means of transits of Venus or 
afford’, other method. Such an opportunity might possibly 
im an improved value of the mass of the earth. 
th 7 following elements of the comet have been computed at 
€ Observatory by Messrs. Safford and Hall. 
Elements of Comet Il, 1861. By T. H. Sarrorp. 
T=1861, June 11.1878, Cambridge m. t. 
log. g= 991299 
n—Q=o 329° 40"81 
= 278 59°28 
: 4 = 85 41°43 
Motion direct. 
By A. Haut. 
T=June 11.280. Washington m. t. 
bed — 248° 51! 50” 
Q = 278 59 23 
a = 85 41 27 
log. g= 991352 
Motion direct. 
From the above, Mr. Safford finds the following approximate 
eae for 105 24m m, t, Washington, 4 and-r representing 
e distances from the earth and sun respectively. 
1861. é log. df log. r 
July 5, 178° 40" 466° 8’ 9°3404 9:9716 
6, 8 21 64 45 
is 195 24 63 13 9°4281 9°9800 
8, 200 37 61 42 
9, 204 34 60 18 9°5051 9°9887 
10, 207 39 50.2 
ll, 210 5 57 54 9°5722 9°9975 
12, 212 56 52 
