VARIOUS INVENTORS. 373 



Some eminent minds did not stop short at this meagre 

 reflection. They conceived that mechanical forces, as 

 well as human passions, must become useful or injurious, 

 according as they are well or ill directed. In the special 

 instance of steam, the simplest arrangement suffices to 

 adapt this redoubtable elastic power to productive labour ; 

 which, according to all appearances, shakes the earth from 

 its very foundations, which surrounds the furnace of the 

 statuary with real dangers, and which shatters the thick- 

 est bomb into a hundred fragments ! 



In what state does this projectile exist before its ex- 

 plosion ? The lower part contains some very hot water, 

 but still fluid ; the rest of the cavity is filled with steam. 

 This steam, it being the characteristic trait of all gaseous 

 substances, exerts its action equally in every direction : 

 it presses with similar intensity on the water and on the 

 metallic envelope that contains it. Let us apply a tap to 

 the lower part of the bomb. As soon as it is open, the 

 water, being urged by the steam, will rush out with ex- 

 treme swiftness. If the tap opens into a tube, which, 

 after curving round the exterior of the shell, rises up ver- 

 tically, the water, being forced to change its course, will 

 rise up in the tube in proportion to the elasticity of the 

 steam ; or, for it is the same thing though in other words, 



Rivault I have not gone back far enough ; if he were to borrow a quo- 

 tation from Alberti, who wrote in 1411 ; if, according to that author, 

 he were to tell us that from the beginning of the fifteenth century, the 

 lime-burners feared much for themselves and their kilns, from the ex- 

 plosion of pieces of limestone fortuitously containing some cavities, I 

 should answer that Alberti himself was ignorant of the real cause of 

 those terrible explosions, for he attributed them to the air in the small 

 cavities being transformed into steam by the action of flame. I must 

 remark, in conclusion, that a piece of limestone, accidentally hollow, 

 would not have afforded the means of numerical appreciation of which 

 Rivault's experiment seems susceptible. 



