234 M. Arago's Biographical Memoir of James Watt. 



art, would remain dumb before the man who would ask him 

 in general terms, who was the inventor of the watch. The 

 question, on the contrary, would occasion him but little em- 

 barrassment, if directed separately to the spring, to the differ- 

 ent forms of the escapement, to the balance wheel, &c. So 

 it is with the steam-engine : it now exhibits the realization of 

 various capital but wholly distinct ideas, which could not have 

 emanated from the same source, and of which it is now our 

 duty to search carefully for the origin and the date. 



If to have employed steam in any way whatever confers a 

 right, as has been pretended, to figure in this history, we 

 must cite the Arabians in the first rank, since, from time 

 immemorial, their principal food, the pudding, which they 

 call couscoiissou^ is boiled by the action of steam in drainers 

 placed upon their rude pots. Such a conclusion shews only 

 the absurdity of the principle from which it is deduced. 



Our compatriot Gerbert, who afterwards wore the triple 

 crown under the name of Silvester IL, — had not he, it may 

 be inquired, a superior claim, when, in the ninth century, he 

 made the organ of the Rheims Cathedral resound by means of 

 steam ? I think not. For in the instrument of the future 

 Pope, I see nothing more than a current of steam substituted 

 for the common current of air, so producing the musical phe- 

 nomena of the organ pipes, but without accompUshing any 

 mechanical effect properly so called. 



I find the first example of motion produced by steam in a 

 toy much more ancient than the organ of Gerbert, viz. in the 

 Eolipyle of Hero of Alexandria, the date of which ascends to 

 120 years before ovir era. It will perhaps be difficult, without 

 the help of figiu*es, to give a clear conception of the mode in 

 which this little piece of apparatus acts ; but I shall neverthe- 

 less make the attempt. When a gas escapes in a given direc- 

 tion from the vessel which contains it, this vessel has a ten- 

 dency to move in a diametrically opposite direction, owing to 

 the force of the reaction. The recoil of a musket when dis- 

 charged is nothing more than this. The gas produced by the 

 inflammation of the saltpetre, charcoal, and sulphur, issues into 

 the air in the direction of the barrel ; that direction prolonged 

 backwards, abuts at the shoulder of the person who has dis- 



