OF ARTS AND SCIENCES: MAY 24, 1864. 309 



upon subjects only indirectly related to the science, would perhaps 

 furnish the titles of scarcely the half of his published writings ; but they 

 include those by which his name has been most widely known. His 

 celebrated criticisms upon the theory of the planetary perturbations, as 

 developed in the Mecaniqiie Celeste, where he boldly called in question 

 the authority of Laplace upon a subject which had afforded to that 

 renowned geometer one of the most brilliant of his triumphs, were 

 alone sufficient to show his confidence in his own powers, and to place 

 hira in a position of prominence before the scientific world which only 

 abilities of the highest order could have sustained ; nor was this the 

 only occasion on which he exercised great freedom of criticism in 

 charging theoretical errors upon the same author. 



His attention seems to have been early directed to the Lunar Theory. 

 Already in 1813 he was seriously contemplating its discussion in con- 

 junction with Carlini. The principle on which it was proposed to 

 conduct this discussion may be designated as the literal solution of 

 the problem, where the coefficients of the inequalities are expressed 

 in theoretical form, in contradistinction to the numerical solution, in 

 which they are derived from observation. Plana zealously maintained 

 the former method to be the only solid basis of the Lunar Theory, 

 even carrying the fervor of his advocacy to the extent of charac- 

 terizing the rival system, exhibited in its highest perfection in the 

 Lunar Tables of Hansen, as " un pas retrograde sous le rapport de 

 la theorie." 



In 1820, a prize, suggested by Laplace, was announced by the 

 Institute for the construction of Lunar Tables, so far as possible, from 

 theory alone. This was adjudged in 1828, by a commission consisting 

 of Laplace, Burckhardt, and Poisson, to be divided between Plana, 

 Carlini, and Damoiseau. The memoir of Plana and Carlini has never 

 been published, but it was probably incorporated, to a considerable 

 extent, in the " Theorie du Mouvement de la Lune," published by 

 Plana in 1832, — a monument of genius and of the most indefatigable 

 industry, triumphing over difficulties of which, to use his own words, 

 it is impossible to form the least conception " sans avoir soi-meme 

 parcouru I'immense ocean qui s^pare le point de depart et le point 

 d'arrivee." 



A supplement to the "Theorie de la Lune" appeared in 1857 ; and 

 he was still vigorously prosecuting, in his eightieth year, the investiga- 

 tions entered upon almost half a century earlier. Even at a still later 



VOL. VI. 32 



