INTRODUCTION. 



We must not forget also that machines which owe their motion 

 to the elastic force of steam, have not limited their services, in 

 the century in which they have been invented and improved, to 

 direct production. They have rendered possible the more perfect 

 manufacture of all other machines and of a multitude of appliances 

 and tools, without which a hundred industries would in the present 

 day be either abolished or reduced to the rudest of primitive methods 

 of production. 



In industry, then, this is what would happen by the suppression 

 of the steam-engine. But what confusion this suppression would 

 also bring about in our commercial and other relations? At the 

 present time steam is the great carrier. What would happen if 

 suddenly the 300,000 or 400,000 kilometres of existing railways 

 were to cease working, and if steamships no longer continued their 

 customary journeys on the rivers, canals, arid seas ? 



I have purposely chosen as an example of the applications of 

 science one which has transformed, in the deepest and most uni- 

 versal way, the conditions of labour and of international and 

 national relations. But, by making a similar supposition with 

 regard to each of the principal modern inventions, if the conse- 

 quences were not operative on such a large scale, still it would 

 not follow that they would be less obvious to each of us. We 

 have at the present time a thousand habits, a thousand wants, 

 which would be satisfied with difficulty, were the inventions to be 

 abolished which have caused them little by little to exist. This 

 each of us can easily verify for himself by considering all those 

 things which surround him w T hich are, directly or indirectly, con- 

 nected with an invention or an improvement which had science 

 for its origin. The account of the principal applications described in 

 this work, although restricted to one science, that of Physics, will 

 clearly prove the truth of the statement we have just dwelt upon. 



II. 



Let us follow the natural order of the subject, an 

 with the scientific applications of the fact that bodies 

 These are, with few exceptions, at once the most anciently 

 and the most generally employed. 



B 2 



