since, according as
it _bulged in or out_ under the disturbing influence of the planets, the
passage of the comet was affected _inside_ or _outside_ the terrestrial
track. Now, certain calculations published by Olbers in 1828[255] showed
that, on October 29, 1832, a considerable portion of its nebulous
surroundings would actually sweep over the spot which, a month later,
would be occupied by our planet. It needed no more to set the popular
imagination in a ferment. Astronomers, after all, could not, by an
alarmed public, be held to be infallible. Their computations, it was
averred, which a trifling oversight would suffice to vitiate, exhibited
clearly enough the danger, but afforded no guarantee of safety from a
collision, with all the terrific consequences frigidly enumerated by
Laplace. Nor did the panic subside until Arago formally demonstrated
that the earth and the comet could by no possibility approach within
less than fifty millions of miles.[256]

The return of the same body in 1845-46 was marked by an extraordinary
circumstance. When first seen, November 28, it wore its usual aspect of
a faint round patch of cosmical fog; but on December 19, Mr. Hind
noticed that it had become distorted somewhat into the form of a pear;
and ten days later, it had divided into two separate objects. This
singular duplication was first perceived at New Haven in America,
December 29,[257] by Messrs. Herrick and Bradley, and by Lieutenant
Maury at Washington, January 13, 1846. The earliest British observer of
the phenomenon (noticed by Wichmann the same evening at Koenigsberg) was
Professor Challis. "I see _two_ comets!" he exclaimed, putting his eye
to the great equatoreal of the Cambridge Observatory on the night of
January 15; then, distrustful of what his senses had told him, he called
in his judgment to correct their improbable report by resolving one of
the dubious objects into a hazy star.[258] On the 23rd, however, both
were again seen by him in unmistakable cometary shape, and until far on
in March (Otto Struve caught a final glimpse of the pair on the 16th of
April),[259] continued to be watched with equal curiosity and amazement
by astronomers in every part of the northern hemisphere. What Seneca
reproved Ephorus for supposing to have taken place in 373 b.c.--what
Pingre blamed Kepler for conjecturing in 1618--had then actually
occurred under the attentive eyes of science in the middle of the
nineteenth century!

At a