WILLIAM SIEMENS, F.R.S. 103 



the boiler would meet it. Supposing the initial temperature 

 of the water to be about 70" Fahr., the weight of the condensing 

 water should exceed the weight of the condensed steam about ten 

 times to effect perfect condensation ; the velocity of the united 



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 jet or sheaf would be in this case = -r^ = 155 feet per 



second, or nearly doubly sufficient to force its way into the boiler. 

 It might here be remarked, that the author of the paper was 

 dourly in error when he stated that the steam was only partially 

 condensed in the sheaf. Uncondensed steam encountering water 

 could not drive it back ; but a column of water encountering 

 another column of inferior velocity must drive it back. It was 

 essential that water of sufficiently low temperature should be brought 

 into contact with the jet of steam to effect its entire condensation, 

 without reducing its velocity below the limit indicated by the 

 imaginary velocity of the opposing column. In the case assumed, 

 the weight of condensing water, or of the water injected into the 



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boiler, must not exceed the weight of condensed steam by - - 



78 



= 22 times, or making allowance for losses of effect, say by 18 

 times. Taking the total heat of steam at 1,150 units, it followed 

 that the rise of temperature of the injected water would be 



- = 64 Fahr., and assuming that the final temperature of 

 18 



the sheaf must not exceed 190, in order to effect entire con- 

 densation, it followed that the initial temperature of the injected 

 water mustjiot exceed 190 - 64 -= 126 Fahr. If it should be 

 attempted, under the circumstances, to inject water of a tempera- 

 ture exceeding 120 Fahr., the sheaf must break up, and the action 

 of the instrument be paralyzed. On the other hand, the greatest 

 quantity of water which each pound of steam would be able to 

 take depended upon the relative velocity of steam and water when 

 acted upon by the same pressure, and might be expressed by 



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-^wrr- = 22 Ibs. That would be the greatest quantity of water 



which each pound of steam could urge forward into the boiler, or 

 could urge forward if there were no loss from friction or by the 

 vortices formed. In reality it would probably not deliver much 

 above half that quantity into the boiler. 



