310 Gilliss on the Physical Aspects of the Great Comet of 1861. 
slowly fading away. At these times the dark space between the 
two branches of the coma became more distinct, and the optical 
illusion of a curve in the line of the axis more apparent. The 
most noteworthy of these changes was just at 11 o’clock, shortly 
after which hour the observations ceased. 
July 8.—The nucleus was more planetary than during last 
evening, and was approximately of the same degree of bright- 
ness, or produced the same effect upon the eye as $ Ursee Majoris. 
It became visible soon after 8" Pp. M. 
In the equatorial, and with power 70 as used then, the sector 
head was much more distinct, and its anterior boundary quite 
circular. The posterior line was a caustic, of which the nucleus 
occupied one of thecusps. The eastern cusp. was sharp, whilst 
Upon attempting to compute an orbit for the comet, Prof. 
Hubbard found it impossible to represent the observed path b 
a parabola, and then obtained by the Gaussian method the fol- 
lowing hyperbolic elements, based upon the places obtained by 
Mr, Ferguson on the 2d, 8th, and 17th of July. They give for 
the middle date the values 4/= —0'-33, 4b=—0'"16. 
Time of perihelion passage, 1861, June 11.85294. Wash. M.T. 
Lo 249° 44! 4458 t M. pe bir 
ng. of perihelion, 
“ node, 278 59 49 ‘72 1861°0 
Inclination, 85 56 
Excentricity, 1:0265470 
Perilielion distance, 0°7453901 ; 
The following is the list of observations, as far as reduced and 
compared with the above elements: 
