STEAM. 205 



water. These vaporised waters overcome all obstacles 

 and overturn everything upon their passage." 



Hero of Alexandria, surnamed the Ancient, who 

 lived about 200 B.C., composed several works on 

 physics, only three of which are extant. The reacting 

 engine is defined and represented in the treatise 

 entitled, Spiritalia, seu Pneumatica. 



Description of the Eolip//his ( Gate of Eolus). 

 BY HERO OF ALEXANDRIA. 



This, after the fragment translated into French by 

 M. Egger, is described as follows : 



" A vessel being heated from underneath, a sphere 

 is made to turn upon its pivot. Or else a vessel con- 

 taining water, and with a lid over the orifice. To this 

 lid should be adjusted a tube bent so that one end of 

 it may be embedded in the side of a hollow sphere. 

 Opposite the end of the tube, and following the 

 diameter of the sphere, should be a pivot rising over 

 the lid ; let the sphere be fitted with two small bent 

 ajutages fixed to its side, according to a corresponding 

 diameter, and bent the reverse way the one from the 

 other. Suppose for a moment the elbows of the 

 ajutages upon the vertical plane. Thereupon, the 

 vase being heated, the vapour, ascending into the 

 sphere through the tube, will escape through the 

 ajutages of the elbows above the cover, and will make 

 the sphere move upon its axis, as is done with persons 

 asleep." 



