Once more, in August, 1852, the double comet returned to the neighbourhood of the sun, but under circumstances not the most advantageous for observation. Indeed, the companion was not detected until September 16, when Father Secchi at Rome perceived it to have increased its distance from the originating body to a million and a quarter of miles, or about eight times the average interval at the former appearance. Both vanished shortly afterwards, and have never since been seen, notwithstanding the eager watch kept for objects of such singular interest, and the accurate knowledge of their track supplied by Santini's investigations. A dangerously near approach to Jupiter in 1841 is believed to have occasioned their disruption, and the disaggregating process thus started was likely to continue. We can scarcely doubt that the fate has overtaken them which Newton assigned as the end of all cometary existence. _Diffundi tandem et spargi per coelos universos._[260] Biela's is not the only vanished comet. Brorsen's, discovered at Kiel in 1846, and observed at four subsequent 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 Möller,[264] director of the Swedish observatory of Lund, to exhibit no trace of the action of a resisting medium.