Cometary News. – Astronomers are now on the qui vive for no less than three periodical comets – viz. Faye’s, Encke’s, and the great comet of 1556.  A new claimant for the honour of the discovery of the sixth comet of 1857 has appeared in the person of Mr. Van Arsdale, of Newark, New Jersey, United States.  Unfortunately, his claim, however, does not hold good, since Mr. Van Arsdale did not detect the comet until 7.55 p.m., whereas Mr. Donati first saw it at 7.5 p.m. on the evening of the 11th of November last; and consequently, taking into consideration the difference of longitude between Florence and Newark, the latter gentleman was the prior discoverer by several hours.  We say “unfortunately” since we believe this is not the first occasion on which Mr. Van Arsdale has been compelled to yield the palm of a discovery, by a short interval of time, to another person.  —Illustrated Inventor.