STEAM-BOILERS ELECTRIC MACHINES. l6l 



SUDDEN DISAPPEARANCE OF HEAT FROM CONDENS- 

 ING STEAM. 



Although most of the latent heat of steam 

 becomes manifest by condensation in the pipes of 

 a heating apparatus, yet in operating high-pressure 

 boilers a very sudden and mysterious disappear- 

 ance occurs ; as is manifest by holding the hand 

 in front of the steam issuing from a gauge-cock, 

 with a pressure of seventy pounds to the inch. 

 About thirty years ago an engineer, in reaching 

 out his hand to adjust a leaking valve, felt electric 

 shocks, and saw electric sparks. He narrated the 

 fact to Mr. Armstrong; who constructed a small 

 insulated steam-boiler for experimental use, and 

 in the account of his experiments said : " This 

 boiler excited tenfold more powerful electricity 

 than can be produced by any frictional electric 

 machine hitherto made, giving out sparks more 

 than a foot long." In this way, steam-boilers 

 were introduced to professors of science under 

 the new name of " Hydro-Electric Machines." 

 Armstrong and Faraday ascribed the electric 

 excitation " to the friction of the particles of water 



ise on Steam-Engine, p. 300) as "745,812 foot-pounds;" and the "total 

 heat of combustion of one pound of carbon "as " 11,194,000 foot-pounds." 

 By this estimate, one pound of coal should evaporate about fifteen pounds 

 of water. Mr. Rankine adopts the estimate of combustion of one pound 

 of hydrogen at 14,500 thermal units of 772 foot-pounds = 47,888,704 

 foot-pounds, being fourfold more exciting than one pound of carbon. 

 By ordinary furnaces of steam-engines only a small portion of the theo- 

 retical power is practically attained. 



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