350 LAPLACE. 



The calculation to which I have just alluded, may be 

 cited in support of considerations to which I had recourse 

 when I wished to establish, that if the moon alters more 

 or less the height of the barometer, according to its 

 different phases, the effect is not attributable to attrac- 

 tion. 



No person was more sagacious than Laplace in dis- 

 covering intimate relations between phenomena appar- 

 ently very dissimilar ; no person showed himself more 

 skilful in deducing important conclusions from those 

 unexpected affinities. 



Towards the close of his days, for example, he over- 

 threw with a stroke of the pen, by the aid of certain 

 observations of the moon, the cosmogonic theories of 

 Buffon and Bailly, which were so long in favour. 



According to these theories, the earth was inevitably 

 advancing to a state of congelation which was close at 

 hand. Laplace, who never contented himself with a 

 vague statement, sought to determine in numbers the 

 rapid cooling of our globe which Buffon had so elo- 

 quently but so gratuitously announced. Nothing could 

 be more simple, better connected, or more demonstrative, 

 than the chain of deductions of the celebrated geometer. 



A body diminishes in volume when it cools. Accord- 

 ing to the most elementary principles of mechanics, a 

 rotating body which contracts in dimensions ought inevi- 

 tably to turn upon its axis with greater and greater 

 rapidity. The length of the day has been determined in 

 all ages by the time of the earth's rotation ; if the earth 

 is cooling, the length of the day must be continually 

 shortening. Now there exists a means of ascertaining 

 whether the length of the day has undergone any varia- 

 tion ; this consists in examining, for each century, the 



