On the Great Comet of 1843. 193 
Thus it appears that Plantamour, Nicolai, and Encke on two 
occasions, had encountered the same paradox as ourselves, viz. 
that of a perihelion point within the sun. It is also remarkable 
that none of the orbits except Encke’s hyperbola suffice to rep- 
resent the observed path of the centre of the nebulosity among 
the stars. 
Hence it appears from the concurrence of authorities on these 
subjects, that good observations of the path of the centre of the 
nebulosity, carefully reduced, lead to a hyperbolic orbit, and an 
approach of centres of the sun and comet as near as their physi- 
cal qualities will permit. 
In this stage of the enquiry the principal difficulty consists in 
reconciling these two paradoxes with our favorite opinion of the 
identity of the three comets of 1668, 1689, and this year, with a 
short period of 21% years. Now it is fortunate that in the case 
of our hyperbola the same natural and plausible explanation that 
does away with the one paradox does away with the other. The 
true key to the solution of the difficulty is, we are persuaded, the 
suggestion first made to us by Mr. Herrick, March 28th, and first 
suggested to the public, by ourselves, in the United States Ga- 
zette of April 6th, viz. the ‘uncertainty whether the central or 
densest portion of the nebulosity corresponds with the actual cen- 
tre of gravity.”” We now proceed to state the opinions of our es- 
teemed friends and correspondents on this point. Dr. Anderson 
of New York, writes under date of May 19th and 22d, stating 
unhesitatingly that the analogies in favor of the identity of the 
comets of 1668 and 1689, should lead us to reject the hyperbolic 
orbit as being unnatural in itself, and wholly irreconcilable with 
these analogies. And that we should rather regard this hyper- 
bolic orbit, and too close perihelion distance, as the consequence 
of some error in the data, or in the methods, or in the ecomputa- 
tions. ‘That there is nothing in the effect of contact of the bod- 
ies, or resistance of the comet by the atmosphere of the sun, 
which could change the character of the conic section, from one 
of a less velocity to one of a greater. From Professor Alexander, 
of Princeton College, we have received a letter dated May 20th, 
in which he proposes an explanation of the difficulty at once sim- 
ple and natural, and fulfilling all that was required by Dr. Ander- 
son. It is based on the supposed occurrence of the very error 
against which we were cautioned by Mr. Herrick, March 28th, 
Vol. xty, No. 1.—April-June, 1843. 25 
