Of the five comets of 1874 the third, or comet of Coggia, was alone visible to the naked eye–Telescopic aspect and spectrum of the comet during the early part of its apparition, according to Messrs. Wolf and Rayet–Observations of Secchi, Bredichin, Tacchini, and Wright; polarisation of the light of the nucleus and tail– Transformations in the head of the comet between the 10th of June and the 14th of July, according to Messrs. Eayet and Wolf.

The comets, and not the comet, of 1874 should form the title, strictly speaking, of the present section of our work. Indeed, at the time of adding these lines to this chapter– that is to say, in the last few days of the month of August of this year [1874]–five new comets have been discovered and observed. But one only, the third in order of date, has attracted the attention of the public, for the simple reason that it alone became bright enough during the time of its apparition to be visible to the naked eye. The other four continued to remain telescopic comets, accessible only to professional astronomers. Although its visibility in Europe was of brief duration, the comet of 1874, III., or comet of Coggia, presented in its physical aspect, and in the changes of form in its head and tail, sufficiently curious phenomena to merit special mention and some detailed description.