According to Dr. Smart, the comet will, on June 2, “cross the Equator thirteen degrees south of Regulus, and will then move slowly in the direction of φ Leonis. The comet will be at its descending node on the ecliptic in the morning of May 16, and the earth will pass through the node on the comet’s orbit about two and a half days later. The comet’s orbit at the node is about 13 million miles within that of the earth. Matter repelled from the comet’s nucleus by the sun with a velocity of about 216,000 miles per hour, would just meet the earth when crossing the comet’s orbit plane. Matter expelled with a velocity of 80,000 miles per hour, as in the case of Comet Morehouse, would require seven days for the journey. Cometary matter is said to have acquired greater velocities than this, for (according to Webb, who quotes Chacornac) Comet II., 1862, shot luminous matter towards the sun, with a velocity of nearly 2200 miles per second. It is therefore possible that matter thrown off by the comet at the node may enter our atmosphere, in which case we must hope that cyanogen, which so often appears in cometary spectra, may not be inconveniently in evidence.”[209]
Cyanogen is, of course, a poisonous gas, but cometary matter is so rarefied that injurious effects on the earth need not be feared.
If we can believe the accounts which have been handed down to us, some very wonderful comets were visible in ancient times. The following may be mentioned:—
B.C. 165. The sun is said to have been “seen for several hours in the night.” If this was a comet it must have been one of extraordinary brilliancy.[210]
B.C. 146. “After the death of Demetrius, king of Syria, the father of Demetrius and Antiochus, a little before the war in Achaia, there appeared a comet as large as the sun. Its disc was first red, and like fire, spreading sufficient light to dissipate the darkness of night; after a little while its size diminished, its brilliancy became weakened, and at length it entirely disappeared.”[211]
B.C. 134. It is recorded that at the birth of Mithridates a great comet appeared which “occupied the fourth part of the sky, and its brilliancy was superior to that of the sun.” (?)[212]
B.C. 75. A comet is described as equal in size to the moon, and giving as much light as the sun on a cloudy day. (!)[213]
A.D. 531. In this year a great comet was observed in Europe and China. It is described as “a very large and fearful comet,” and was visible in the west for three weeks. Hind thinks that this was an appearance of Halley’s comet,[214] and this has been confirmed by Mr. Crommelin.
A.D. 813, August 4. A comet is said to have appeared on this date, of which the following curious description is given: “It resembled two moons joined together; they separated, and having taken different forms, at length appeared like a man without a head.” (!)[215]
A.D. 893. A great comet is said to have appeared in this year with a tail 100° in length, which afterwards increased to 200°![216]