296 



On the Rapid Production of Steam 



important. The experiments to determine the period of greatest 

 activity will show, that just below the point of visible redness in day- 

 light, the greatest quantity of steam is generated in a given number 

 of instants. Such at least is the case when the experiment is per- 

 formed under ordinary atmospheric pressure. This point therefore, 

 I have termed in the tables the comparable temperature. Many of 

 the experiments with wrought iron were performed upon a piece of 

 rolled holler plate, 25^ inches long, by 7 J broad, and j\ of an inch 

 thick, affording a surface (including both faces, and all the edges) of 

 three hundred and ninety five square inches. This was reduced to 

 a coil, for the greater convenience in managing the experiments, but 

 sufficient space was left for the free admission of water to every 

 part of the surface. The first series was intended to exhibit the 

 quantity of steam generated without particular reference to the time. 

 The latter however was immediately noted on each occasion, but is 

 not to be taken as the least time, in which the mass of metal em- 

 ployed could impart its surplus heat to boiling water. It serves to 

 show that no essential difference was discoverable in the amount of 

 steam produced by metal of the same temperature, whether the lat- 

 ter were immersed all at once, or only covered by degrees with the 

 water, and that, consequently the portion of overheated surface which 

 remained above the water, did not impart to the steam which ascen- 

 ded, any appreciable quantity of its caloric, during the experiment. 



FIRST SERIES, 



With rolled iron, 395 square inches of surface — water at 212° Fall, ; 

 barometer, 29.9 inches ; the time marked by a pendulum beating 

 seconds ; temperature of the apartment from 80° to 85°. 



