M. Chacornac's observations upon the comet of 1862–Formation of luminous sectors emanating from the nucleus–Oscillation of aigrettes, and flowing back of the nucleal matter.

We are now about to give our attention to the evolutions of the luminous sectors of the great comet of 1862, which, on the contrary, presented oscillations analogous to those exhibited by the aigrettes of Halley's comet. We shall follow the development of these phenomena by means of the observations of the late M. Chacornac.

On August 10, 1862, M. Chacornac detected in the head of the comet the presence of a luminous aigrette, a brilliant sector directed towards the sun. This sector, which at three o'clock in the morning included an angle of 46°, had, by two o'clock on the following day, opened ‘ like the corolla of a convolvulus, and included 65°. On the 10th the nucleus presented the appearance of a rocket, having a diameter much more extended in the direction of the radius vector than at right angles to it.’ It is worthy of remark that the contrary was the case with the nuclei of the comets of 1858 and 1861, which were flattened in the direction of the radius vector. On the 11th the two diameters were nearly equal. New sectors disengaged themselves successively from the nucleus, and on August 26 M. Chacornac determined that between the 10th and the 26th they had succeeded each other to the number of thirteen.