Suddenly one of the observers exclaimed that he could see a small comet accompanying the larger one, and we can imagine his friend making some remark concerning defective eyesight. However, when both saw the duplicity of the comet, all doubts were dispersed. But what did it mean? Had the comet a satellite, just as the earth has its accompanying moon, or had the comet actually split in two? However, the twin comets were seen two weeks later by Lieutenant Maury and Professor Hubbard at Washington, D. C., and two days later it came within the ken of European astronomers. Incidentally, three weeks before the twin comets were observed, Mr. J. Russell Hind (England) noticed a peculiar lump near the upper part of the nucleus of the main comet, which may be regarded as the first symptom indicating that something was amiss. On January 15, Professor Challis, then director of Cambridge Observatory (England), had his suspicions aroused when he saw the complete severance of the little comet from the big one, and the description of his experience is best given in a letter he wrote to the president of the Royal Astronomical Society: “On the evening of January 15, when I sat down to observe it [Biela’s comet], I said to my assistant, ‘I see _two_ comets.’ However, on altering the focus of the eyeglass and letting in a little illumination, the smaller of the two comets appeared to resolve itself into a minute star, with some haze about it. I observed the comet that evening but a short time, being in a hurry to proceed to observations of the new planet.” Presumably he here refers to the search for Neptune. Alas! had he but given his whole attention to that task, instead of dispersing his energy—as it were—by pursuing a flimsy comet, England might have been acknowledged as first in the actual discovery of that planet. Resuming his observations of the comet on January 23, Professor Challis again saw two comets, but clouds hid them from view for the next half-hour, and when they had cleared away he was convinced that the comets had moved during the interval. This suspicion was afterward confirmed, and, moreover, Professor Challis found that they had moved in unison, retaining their relative positions meanwhile. He wondered what could be the meaning of this strange procedure, and whether they were two independent comets, a double comet, or that his glass was deceiving him. “But I never heard of such a thing,” wrote Professor Challis. “Kepler supposed that a certain comet separated in two, and for this Pingré said of him, ‘_Aligreando bonus dormitat Homerus._’ I am anxious to know whether other observers have seen the same thing.” In a subsequent letter he shows by his remarks that “the two comets are not only apparently, but really near each other, and that they are physically connected.”[6]