390 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK iv. 



with greater or less rapidity in the opposite direction from that in 

 which the steam issues. 



The eolipyle (which signifies an eoliaii or air opening) is, as we 

 have seen, a machine where the elastic force of the steam works by its 

 reaction. It has never been more than an amusing physical toy, in 

 spite of its having attracted the attention of savants and of experi- 

 mentalists before the time of Papin, and of a proposal being made to 

 utilize it for turning jacks. 



Some thirty years ago, however, Sir Arthur Cotton succeeded in 

 driving the fan for the air-blast of an iron-founder's furnace by means 

 of one of these engines, and has during the present year (1876) been 



FIG. 270. The eolipyle of Hero of Alexandria. FIG. 271. Solomon de Caus's apparatus' 



making further experiments with a view of applying the principle to 

 useful purposes. 



The apparatus described by Solomon Caus in his pamphlet, Les 

 Raisons des Forces Mouvantes (1605), is a more direct example of the 

 application of the expansive force of steam. Water is introduced by 

 the tap, D, into the hollow sphere, A, which is placed on the fire after 

 closing the tap. A tube, BC, passes by another opening, B, into the 

 water, without touching the bottom. When the steam has been gene- 

 rated in a sufficiently large quantity, arid its tension is great enough, 

 the tap of B is opened, and the water, pressed upon at its upper 

 suriace by the elastic force of the steam, is forced out of the tube. 



