2 Reynolds, Dryness of Saturated Steam. 



by the steam, the steam so withdrawn being condensed 

 in a calorimeter back again to water at any constant 

 temperature. The results proving that the total amount 

 of heat given up by the steam for each temperature in 

 the boiler is consistently proportional to the weight of 

 steam condensed. 



It thus appears that the density of saturated steam at 

 constant temperature must be constant, and that gravity 

 alone is sufficient to free the saturated steam from any 

 water that may have been entangled with it by the action 

 of boiling, provided the rate of flow over the surfaces is 

 not sufficient to carry along with the steam any water 

 there may be on the surfaces. It was only after the 

 utmost care in securing these conditions that Regnault 

 succeeded in obtaining consistent results — which results 

 have since been confirmed by many researches, including 

 that of Messrs. Harker and Hartog read before the 

 Society last year. 



It is to be noticed that the whole theory of the proper- 

 ties of steam, as at present accepted, and all the steam 

 tables are founded on these experiments of Regnault's 

 on the total heat of evaporation, so that if any other 

 definition is given of dry saturated steam, than that of 

 the vapour of water which results from boiling the water 

 under constant pressure after it is drained of entangled 

 water by gravitation, these properties and tables will not 

 apply. 



Wet Steam. 



For the most part the precautions taken by Regnault 

 are precisely those under which steam is produced in 

 practice. That is to say, in practice the conditions in 

 the boiler are maintained, as far as practicable, steady, 

 and the steam is withdrawn in a vertical direction from 

 the steam space over the water, where it is drained by 

 gravitation. Owing, however, to exigencies as to space 



