IO2 



by a jet on a solid surface was equal to double the pressure due to 

 the area which produced it ; but he thought it might be shown, 

 that the jet produced by the steam possessed a very much higher 

 velocity than a jet of water produced by the same pressure which 

 would come out to meet it from the boiler. Thus the steam from 

 the boiler issued with a velocity v = 8 Jh, or nearly so, neglecting 

 the error arising from the circumstance of its being an elastic 

 fluid ; while the water of the boiler would issue with a velocity 

 represented also by the formula v' = 8 Jti ; but the pressure being 

 the same in the two cases, it followed that the height of the column 

 h was superior to h' in the proportion of the relative densities of 

 steam and water. Hence the velocity v of the steam would exceed 

 the velocity v' of the water in the proportion of *J/t : *J~R, or in the 

 case of steam of four atmospheres' pressure, v\v'= Jl : ^47 7, 

 water being 477 times denser than steam of that pressure, or 

 v : v' = 1 : 21-8. 



It was therefore evident, that every particle of steam rushed 

 forward with a velocity nearly twenty-two times greater than that 

 with which the water could meet it, only if it were to rush forward 

 in its elastic state, it was evident that each particle of steam would 

 have to encounter 477 particles of water within the same volume, 

 and must be forced back notwithstanding its superior velocity. 



But if the steam were imagined to be condensed between the 

 point of issue and that of its meeting with the jet of water, if, for 

 instance, its elastic force could be destroyed by making it pass 

 through an infinitely cold space, then the result would be a very 

 contracted jet of water passing forward with the extraordinary 

 velocity of v' = 8 *Jh' = 8 ^/477 x 3 x 32 = 1712 feet per second, 

 meeting a column of v 8 Jh = 8 *J3 x 32 = 78 feet per second. 



The effect would be, that the column of water resulting from 

 the condensation of the steam would pierce the comparatively 

 sluggish jet of water meeting it, as though it were a steel wire 

 forcing its way into the boiler. This was, however, an impossible 

 position, for the steam could not be condensed by itself spon- 

 taneously. But the injector effected the spontaneous condensa- 

 tion of the jet of steam by incorporating with it a sufficient 

 quantity of cold water, which was so regulated, that the mean 

 velocity of the united jet of steam and water still exceeded the 

 velocity of 78 feet per second with which the opposing jet from 



