t returns, failed unaccountably to
become visible in 1890.[261] Yet numerous sentinels were on the alert to
surprise its approach along a well-ascertained track, traversed in five
and a half years. The object presented from the first a somewhat
time-worn aspect. It was devoid of tail, or any other kind of appendage;
and the rapid loss of the light acquired during perihelion passage was
accompanied by inordinate expansion of an already tenuous globular mass.
Another lost or mislaid comet is one found by De Vico at Rome, August
22, 1844. It was expected to return early in 1850, but did not, and has
never since been seen; unless its re-appearance as E. Swift's comet of
1894 should be ratified by closer inquiry.[262]

A telescopic comet with a period of 7-1/2 years, discovered November 22,
1843, by M. Faye of the Paris Observatory, formed the subject of a
characteristically patient and profound inquiry on the part of
Leverrier, designed to test its suggested identity with Lexell's comet
of 1770. The result was decisive against the hypothesis of Valz, the
divergences between the orbits of the two bodies being found to increase
instead of to diminish, as the history of the new-comer was traced
backward into the previous century.[263] Faye's comet pursues the most
nearly circular path of any similar known object; even at its nearest
approach to the sun it remains farther off than Mars when he is most
distant from it; and it was proved by the admirable researches of
Professor Axel Moeller,[264] director of the Swedish observatory of Lund,
to exhibit no trace of the action of a resisting medium.

Periodical comets are evidently bodies which have each lived through a
chapter of accidents, and a significant hint as to the nature of their
adventures can be gathered from the fact that their aphelia are pretty
closely grouped about the tracks of the major planets. Halley's, and
five other comets are thus related to Neptune; three connect themselves
with Uranus, two with Saturn, above a score with Jupiter. Some form of
dependence is plainly indicated, and the researches of Tisserand,[265]
Callandreau,[266] and Newton[267] of Yale College, leave scarcely a
doubt that the "capture-theory" represents the essential truth in the
matter. The original parabolic paths of these comets were then changed
into ellipses by the backward pull of a planet, whose sphere of
attraction they chanced to enter when approaching the sun from outer
space. Mo