338 LAPLACE. 



the principle of universal attraction ; on the other hand, 

 certain irregularities observed in the returns of the moon 

 to the meridian. 



An observing geometer who, from his infancy, had 

 never quitted his chamber of study, and who had never 

 viewed the heavens except through a narrow aperture 

 directed north and south, in the vertical plane in which 

 the principal astronomical instruments are made to move, 

 to whom nothing had ever been revealed respecting 

 the bodies revolving above his head, except that they 

 attract each other according to the Newtonian law of 

 gravitation, would, however, be enabled to ascertain 

 that his narrow abode was situated upon the surface of 

 a spheroidal body, the equatorial axis of which surpassed 

 the polar axis by a three hundred and sixth part ; he 

 would have also found, in his isolated immovable posi- 

 tion, his true distance from the sun. 



I have stated at the commencement of this Notice, 

 that it is to D'Alembert we owe the first satisfactory 

 mathematical explanation of the phenomenon of the 

 precession of the equinoxes. But our illustrious coun- 

 tryman, as well as Euler, whose solution appeared sub- 

 sequently to that of D'Alembert, omitted all consideration 

 of certain physical circumstances, which, how r ever, did 

 not seem to be of a nature to be neglected without ex- 

 amination. Laplace has supplied this deficiency. He 

 has shown that the sea, notwithstanding its fluidity, and 

 that the atmosphere, notwithstanding its currents, exer- 

 cise the same influence on the movements of the terrestrial 

 axis as if they formed solid masses adhering to the ter- 

 restrial spheroid. 



Do the extremities of the axis around which the earth 

 performs an entire revolution once in every twenty-four 



