"The division of Biela's comet into two distinct parts suggests several interesting questions in cometary physics. The nature of the separating force remains to be discovered; 'but it is impossible to doubt that it arose from the divellent action of the sun, whatever may have been the mode of operation.' "'A signal manifestation of the influence of the sun,' says a distinguished writer, 'is sometimes afforded by the breaking up of a comet into two or more separate parts, on the occasion of its approach to the perihelion. Seneca relates that Ephoras, an ancient Greek author, makes mention of a comet which before vanishing was seen to divide itself into two distinct bodies. The Roman philosopher appears to doubt the possibility of such a fact; but Keppler, with characteristic sagacity, has remarked that its actual occurrence was exceedingly probable. The latter astronomer further remarked that there were some grounds for supposing that two comets, which appeared in the same region of the heavens in the year 1618, were the fragments of a comet that had experienced a similar dissolution. Hevelius states that Cysatus perceived in the head of the great comet of 1618 unequivocal symptoms of a breaking up of the body into distinct fragments. The comet when first seen in the month of November, appeared like a round mass of concentrated light. On the 8th of December it seemed to be divided into several parts. On the 20th of the same month it resembled a multitude of small stars. Hevelius states that he himself witnessed a similar appearance in the head of the comet of 1661.'[34] Edward Biot, moreover, in his researches among the Chinese records, found an account of 'three dome-formed comets' that were visible simultaneously in 896, and pursued very nearly the same apparent path. "Another instance of a similar phenomenon is recorded by Dion Cassius, who states that a comet which appeared eleven years before our era, separated itself into several small comets. "These various examples are presented at one view, as follows: "I. Ancient bipartition of a comet.--_Seneca, Quæst. Nat._, _lib. VII. cap. XVI._ "II. Separation of a comet into a number of fragments, 11 B.C.--_Dion Cassius._ "III. Three comets seen simultaneously pursuing the same orbit, A.D. 896--_Chinese records--Comptes Rendus_, tom. xx. 1845, p. 334. "IV. Probable separation of a comet into parts, A.D. 1618.--_Hevelius_, _Cometographia_, p. 341.--_Keppler_, _De Cometis_, p. 50. "V. Indications of separation, 1661.--_Hevelius_, _Cometographia_, p. 417. "VI. Bipartition of Biela's comet, 1845-6.