SPECULATIONS ON THE FORCE OF GRAVITY. 351 



arc of the celestial sphere described by the moon during 

 the interval of time which the astronomers of the exist- 

 ing epoch called a day, in other words, the time re- 

 quired by the earth to effect a complete rotation on its 

 axis, the velocity of the moon being in fact independent 

 of the time of the earth's rotation. 



Let us now, after the example of Laplace, take from 

 the standard tables the least considerable values, if you 

 choose, of the expansions or contractions which solid 

 bodies experience from changes of temperature ; search 

 then the annals of Grecian, Arabian, and modern astron- 

 omy for the purpose of finding in them the angular 

 velocity of the moon, and the great geometer will prove, 

 by incontrovertible evidence founded upon these data, 

 that during a period of two thousand years the mean 

 temperature of the earth has not varied to the extent of 

 the hundredth part of a degree of the centigrade ther- 

 mometer. No eloquent declamation is capable of resist- 

 ing such a process of reasoning, or withstanding the force, 

 of such numbers. The mathematics have been in all 

 ages the implacable adversaries of scientific romances. 



The fall of bodies, if it was not a phenomenon of per- 

 petual occurrence, would justly excite in the highest 

 degree the astonishment of mankind, What, in effect, is 

 more extraordinary than to see an inert, mass, that is to 

 say, a mass deprived of will, a mass which ought not to 

 have any propensity to advance in one direction more 

 than in another, precipitate itself towards the earth as 

 soon as it ceased to be supported ! 



Nature engenders the gravity of bodies by a process 

 so recondite, so completely beyond the reach of our 

 senses and the ordinary resources of human intelligence, 

 that the philosophers of antiquity, who supposed that 



