On the Rapid Pruduction of Steam. 295 



portion of water lost only 31^, being found at 84° thongh the temper- 

 ature of the air had in the mean time fallen to 76°. On another 

 occasion, the loss was 9° per hour, or from 212° to 104° in twelve 

 hours, in an apartment where the air was at 60°. 



The vessel above described charged with about 1 5lbs. of water, was 

 suspended to one hook of the scale beam, while to the opposite was at- 

 tached the usual pan for weights. The water was then brought to a 

 state of rapid ebullition by heaters, previously plunged for an instant in- 

 to another vessel of water, to take off any portion of ashes or oxide 

 which might accidentally adhere to the surface. When assured that 

 the water and its container had acquired the boiling temperature, I 

 replaced the cover, and immediately adjusted the weights to an ex- 

 act counterpoise. The piece of hot metal whose power of produ- 

 cing steam was to be ascertained, was upon removing the cover im- 

 mediately plunged into the boiling water, and permitted to remain 

 until ebullition ceased. At that instant, the metal was withdrawn, the 

 time noted, the lid adjusted and weight added on the side of the boil- 

 er, to compensate for the evaporation of water, until the equilibrium 

 was restored. The experiments were conducted with all due cau- 

 tion to avoid the waste of water, which might ensue from the violent 

 agitation, caused by plunging the metal all at once below the surface. 

 The metal was either lowered gradually into the water, or, when plun- 

 ged in immediately, was suspended to a wire, attached above to a 

 cover, perforated with numerous holes, to allow the escape of steam, 

 and furnished with a broad funnel shaped rim to receive and return 

 any water which might be projected through the apertures. 



In order to avoid communicating to the apparatus a temperature 

 above that of the liquid, the metal was suspended in the water, and 

 not allowed to touch the sides or bottom of the cylinder. 



The difficulty of ascertaining with precision the temperatures 

 above the boiling point of mercury, (660°) compelled me to adopt 

 as a standard of comparison, between the different metals, and be- 

 tween different masses of the same metal, a point indicated by the 

 senses. A barely red heat in daylight was chosen, as least liable to 

 be misapprehended. Many experiments have been made at tem- 

 peratures both above and below this point ; but as it is probable that 

 the heated parts of boilers are seldom raised above a dull red heat, 

 and that if they were so, their danger, or (perhaps we might say) 

 their safety, would arise from the softness and yielding condition of 

 the metal, it has been thought that for practical as well as theoretical 

 purposes, the point above mentioned would be most interesting and 



