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138 and the unusual, and, so to speak, artistic conformation of its tail, which features the absence of the Moon in the early part of October enabled spectators to view to the very best advantage. The passage of the comet in front of Arcturus on Oct. 5 will ever remain treasured in the memory of those

DONATI'S COMET, 1858, PASSING ARCTURUS ON OCT. 5.

who saw it. There is no doubt that Donati's Comet revolves in an elliptic orbit, the period of which has been variously estimated at 1879, 2040, and 2138 years, and Kritzinger thinks it may be identical with a great comet which is recorded by Seneca as having appeared in 146, and dated by the Chinese for the month of August in that year.