TIIK MECANIQUE CELKSTK. 273 



of astronomical refractions ; the determination of heights by 

 the barometer ; the investigation of the effects produced on 

 the movements of the planets and comets by a resisting me- 

 dium ; and the determination of the values of the masses of the 

 planets and satellites. In the six books forming the fifth 

 volume of the work, the author, besides presenting his readers 

 with an historical exposition of the labours of Newton and his 

 successors on the theory of gravitation, gives an account of 

 various researches relative to the system of the universe, 

 which had occupied his attention subsequently to the publi- 

 cation of the previous volumes. In the eleventh book he 

 considers the subjects of the figure and rotation of the earth. 

 In the twelfth book he investigates the attraction and repul- 

 sion of spheres, and the laws of equilibrium and motion of 

 elastic fluids. The thirteenth book is devoted to researches 

 on the oscillations of the fluids which cover the surfaces of 

 the planets ; the fourteenth, to the subject of the movements 

 of the celestial bodies around their centres of gravity ; the 

 fifteenth, to the movements of the planets and comets ; and 

 the sixteenth, to the movements of the satellites. The author 

 published a supplement to the third volume, containing the 

 results of certain researches on the planetary theory, and a 

 supplement to the tenth book, in which he investigates very 

 fully the theory of capillary attraction. There was also pub- 

 lished a posthumous supplement to the fifth volume, the 

 manuscript of which was found among his papers after his 

 death. 



