Page:The story of the comets.djvu/138

98 direction coincided with that of the axis of the nucleus. This direction was almost exactly identical with that of the axis of the tail. On January 20 the nucleus and the nebulosity which surrounded it had resumed their accustomed aspect. I observed the comet up till the end of the 1st week in February without being able to detect any changes like that which happened on Jan. 19. It follows therefore that the transformations in question must have run their course in a few hours; and herein consists the remarkable character of the whole phenomenon."

PONS'S COMET: JAN. 19, 1884. (Trépied.)

Trépied's observations accord generally with those of Perrotin, Thollon, and Rayet, which apply, however, to the date of Jan. 13. It would appear from these various observations, taken together, that this comet underwent changes which, whatever their nature, were in some sense periodic—a circumstance additionally remarkable.