On the Great Comet of 1843. 191 
three comets, and short period of 21%-years, would be untenable. 
Although we considered the hyperbolic orbit as well as the small 
perihelion distance to be both paradoxical, we were willing to 
submit them as genuine deductions from our observations and 
computations, and leave them to be received as paradoxes, or ex- 
_ plained away as the sequel should show. In so doing, we post- 
poned for the time urging our favorite theory of the short period 
of 21% years. It is true that we had suggested the probable cause 
of the acceleration of the comet’s place for the middle observation 
as computed from a parabolic ephemeris, to be owing to the 
shape of the comet, in the United States Gazette of the 6th of 
April, after pointing out the acceleration of the comet’s place for 
the middle observations, viz.* ‘The slight difference between 
the two curves (our parabola and the true path of the comet) is 
lost amidst the errors of observation, and the uncertainty whether 
the central portion or the densest part of the nebulosity corres- 
ponds with the actual centre of gravity.” We were aware that 
Encke had resorted to this hypothesis, to explain the paradox of 
the acceleration of his comet, previous to his more fortunate sug- 
gestion of the resisting medium. In regard to the recent comet, 
our attention was early called to this source of error by our: es- 
teemed correspondent Mr. E. C. Herrick, of New Haven, who, in 
a letter addressed to S. C. Walker, on the 29th of March, remarks, 
“The concentration of light in the nucleus (as seen in the 10 
feet Clark Telescope of 5 inches aperture) seemed to me on two 
occasions to be iderably nearer the anterior than the posterior 
e could detect three dim starlike points, 
but it was almost impossible to decide with certainty. Where 
the tail is so immense; is there not some hazard in assuming the 
centre of the nucleus to be the centre of gravity of the whole body ?” 
We are particular about the-dates of these suggestions respecting 
the centre of gravity of the comet and tail, in as much as it is 
found to bea matter of much importance in the sequel. Having 
fairly on the 19th and 20th laid our two paradoxes, viz. the hy- 
perbolic orbit, and the perihelion distance less than the sun’s 
semidiameter, before the public, with some suggestions as to the 
inferences that would follow from a strict interpretation of this 
result of calculation and observations, viz. that of the necessity 
* See Mr. R. W. Haskins’s paper on the “ Resisting Medium” in this Journal, 
Vol. xxx111, p. 19. 
