tance between the earth and the sun. The last stage of development was when the comet approached Venus. The nearest approach to this planet was on the 17th October, when the distance was only one-ninth the distance between the earth and the sun. Two days before this, a new set of phenomena presented themselves, in the form of comma-like curved appendages to the nucleus, as if formed of bright burning matter, which had been projected from the nucleus, and then twisted back again.
The next inquiry is, How is this extraordinary development produced? What are the forces brought into play? The jet of luminous matter from the centre, is naturally explained by the action of the sun's heat, for the action is energetic in proportion to the nearness of the comet to the sun. The grand difficulty is the throwing back of the matter into the tail. Father Secchi thinks that it can be explained by the unequal action of gravitation on different parts of the comet, and holds that the distortions produced on the approach to the earth and Venus corroborate this view. It is evident that there is some repelling power, and a power capable of communicating an inconceivable velocity to the repelled particles. The usual method is to ascribe it to electric or magnetic action. It is ascertained that the sun and the moon, as well as the earth, are magnets; and the great probability is, that all the heavenly bodies are magnetic. This seems to afford a plausible ex-
