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The Story of the Comets.
Chap.
the side opposite to the Sun. From this side also the head of the comet divided itself into two distinct parts forming the commencement of the tail: for some distance this bifurcation was remarkably sharply defined, suggesting an intense repulsive force acting upon the nucleus of the comet; and the space enclosed between this bifurcation was strikingly free from nebulous matter,until at some little distance away from the nucleus the sharp definition faded into the general nebulosity of the tail."
The following remarks on this comet are by two French observers, MM. Wolf and Rayet:—
"After having maintained for many days a great sameness of form, on June 22 a series of changes in the shape of the head of the comet commenced. On that day the comet, viewed with a Foucault telescope of 40 centimetres, appeared to be enclosed in the interior of a very elongated parabola. Starting from the nucleus, which was placed as it were at the focus of the curve, the brightness decreased gradually towards the summit: but in the interior of the parabola the diminution of the brightness was sudden, and the boundary-line exhibited another parabola a little more open than the first, and having at its own summit the brilliant nucleus itself. The outline of the parabola which passed through the nucleus was prolonged so as to form the lateral boundaries of the tail, the edges of which were well defined and were much brighter than the interior parts. This tail had then the appearance of a luminous envelope hollow in the inside. The nucleus was always very sharp. On July 1 the general form of the comet remained the same; it appeared always to possess a parabolic outline at its exterior edge. The nucleus, however, jutted out into the interior of the second parabola, and the opposite margins of the tail were not strictly symmetrical. The West side, that is to say the side which had the greatest R.A., was very sensibly brighter than the other. . . . From July 5, the want of symmetry spoken of above became more and more marked, and near the head the decrease of the brightness became less regular. On July 7, the contrast between the two branches was striking, the Western branch of the tail being about twice as bright as the Eastern. At the same time the nucleus appeared to be becoming diffused, and it seemed to fade away in the direction of the head of the comet, although still sharply defined on the side nearest the tail; one could not fail to remark its resemblance to an open fan. . . . Our last observation of the comet was made on July 14 at 9.30 p.m.: important changes in the aspect of the head had manifested themselves. The fan of light had disappeared on the West side, and was replaced by a long spur of light which was traceable for a considerable distance across the head; on the West side the remnant of the fan terminated abruptly, and the boundary-line there made but a small angle with the main axis of the comet. On this same occasion two rays of light were visible—two jets as they might be deemed—thrown forwards, the one to the right and the other to the left; these luminous rays seemed to have their origin at the edge of the fan of which they formed a sort of prolongation. The ray which pointed towards the East projected well forwards, and being bent round towards the tail soon reached the preceding edge of the comet; it was faint and hardly surpassed the nebulosity in brilliancy. The ray projected towards the West was much more brilliant, and was similarly
