forgeries; but there appears to have been no sufficient ground for this imputation, and it was eventually withdrawn. It remains to be added that the comet passed its perihelion on March 12, 1759—just within the limits assigned by Clairaut. After that, it was seen throughout Europe during April and May, although to the best advantage only in the Southern Hemisphere. On May 5, it had a tail 47° long.
Previous to the return of the comet in 1835, numerous preparations were made to receive it.
The great progress which had been made since 1759 in telescopes and methods of observation, especially under the inspiration of the two Herschels, Sir William and Sir John; and also in mathematics applied to celestial motions by men like Laplace, Lalande, La Grange, and other eminent foreigners, rendered the study of the movements of this comet, both visually when the time came to see it, and mathematically, before that time, a problem of great interest. As long before the expected return of the comet as 1817 the Academy of Sciences at Turin offered a prize, open to astronomers of all nations, for an Essay on the perturbations undergone by the comet since 1759. Baron Damoiseau of Paris gained the prize, and his Essay was published in 1820 in the Memoirs of the Turin Academy, vol. xxiv. The following outline of the researches of Damoiseau and others is epitomised from Hind's statement of them.
After calculating the effects of the attraction of the larger planets he fixed Nov. 4, 1835, at 8 p.m., Paris M.T., as the moment of the comet's perihelion passage. After Damoiseau, another Frenchman, Count de Pontécoulant, took up the matter, more or less on the same lines as Damoiseau, with the result that his date for the perihelion was rather more than a week later than Damoiseau's, or to be exact, he fixed the perihelion for Nov. 12, at 17h , Paris M.T. The investigations both of Damoiseau and Pontécoulant were in a sense defective because both of them had omitted to take account of certain of the planets whose influence counted for something. Accordingly a German computer, Rosenberger of Halle, started on a new and independent investigation.
