ASTRONOMY OF EIGHTEENTH CENTURY. 267 



of certain scientific problems, but also in its application to political 

 and economic questions. Such matters as annuities, life assurances, 

 policies, etc., are obvious instances. But the attempt has so been 

 made of submitting to mechanical analysis the probabilities of legis- 

 lative councils, juries, courts, etc., arriving at given conclusions. Many 

 questions affecting commercial speculations are more amenable to 

 treatment by the doctrine of probabilities, and the hazards in a game 

 of chance can of course be accurately estimated. 



PIERRE SIMON LAPLACE was born in 1749 near Honfleur. At an* 

 early age he distinguished himself for his mathematical ability, and 

 when, by the influence of D'Alembert, he was appointed to the pro- 

 fessorship of mathematics in the MiHtary School at Paris, he began to 

 plan the great work to which he devoted the best part of his life and 

 all the powers of his genius. His object was nothing less than to in- 

 terpret the whole mechanism of the universe. Laplace did not create 

 a new science, like Galileo, nor did he add a new calculus to our ma- 

 thematics, like Descartes or Leibnitz ; but he collected and arranged 

 all that was known on the mechanism of the universe ; he traced the 

 doctrine of gravitation to its ultimate consequences ; and he reduced 

 a vast range of the truths of physical science to the dominion of ma- 

 thematical knowledge. 



Though Newton pointed out the nature and general results of the 

 forces interacting between the bodies of the solar system, he did not 

 trace out all the effects which those forces produce. The immense 

 complication produced by the actions and reactions of so many bodies, 

 and the changes of their positions and velocities, outstripped the powers 

 of geometry to unravel. So numerous were the varieties of direction 

 and intensity of the different forces, that the maintenance of perma- 

 nent equilibrium, under conditions so changing, appeared a miracle ; 

 and Newton supposed that a superior power must from time to time 

 intervene to restore the order and stability of the system. Euler, who 

 had obtained a more extended knowledge of the perturbing actions of 

 the planets upon each, also refused to admit that the solar system 

 contained within itself the principle of permanent stability. It had 

 been found by comparing ancient observations with modern ones that 

 the motion of the planet Jupiter was being constantly accelerated, 

 and that the motion of Saturn was undergoing a diminution. The 

 inference from the supposed cause of these changes was that the 

 former planet was approaching the sun, and that the latter was reced- 

 ing. The amount of these changes was not great, but their existence 

 was undoubted ; and it seemed perfectly just to conclude that the 

 magnificent planet Jupiter would finally plupge into the sun, while the 

 mysterious Saturn, with its ring and seven satellites, would gradually 

 withdraw from our system and pass away into the depth of space. 

 Again, there was the undeniable secular acceleration of the moon, 

 which appeared inevitably destined to end by our satellite being pre- 



