THE SCIENTIFIC SPIRIT IN FRANCE. 123 



to grasp practical issues, and always descending into in- 

 finitesimals. It is hardly to be doubted now, after the 

 lapse of a century, that the infinitesimals of Laplace play 

 a more important part in problems of administration and 

 government than the ideas of ISTapoleon. Laplace, un- 

 like some other great scientific thinkers, attached great 

 value to a popular exposition of the principles of his dis- 

 coveries. Descartes required a Fontenelle and Newton a 

 Voltaire to make their ideas accessible and useful to the 

 mass of students. Laplace was his own Fontenelle and 

 Voltaire. " Few works," says Sir John Herschel, " have 

 been more extensively read, or more generally appreciated, 

 than Laplace's ' Essai philosophique sur les Probabilites,' 

 and that on the ' Systeme du ]Monde ' by the same author. 

 It is not, perhaps, too much to say that were all the 

 literature of Europe to perish, these two essays excepted, 

 they would suffice to convey to the latest posterity an 

 impression of the intellectual greatness of the age which 

 could produce them, surpassing that afforded by all the 

 monuments antiquity has left us. Previous to the pub- 

 lication of the ' Essai philosophique,' few, except professed 

 mathematicians or persons conversant with assurances 

 and similar commercial risks, possessed any knowledge of 

 the principles of this calculus, or troubled themselves 

 about its conclusions, regarding them as merely curious 

 and perhaps not altogether harmless speculations. Thence- 

 forward, however, apathy was speedily exchanged for a 

 lively and increasing desire to know something of a system 

 of reasoning which for the first time seemed to afford a 

 handle for some kind of exact inquiry into matters no one 

 had ever expected to see reduced to calculation, and bear- 



