Processes in the Useful Arts. 167 



111 reference to high temperatures. If any part of the boiler which con- 

 tains the steam be suffered to become of a higher temperature than the 

 water contained in it, from want of a sufficient supply, the steam will 

 readily receive an excess of caloriCj and become supercharged with it, with- 

 out acquiring proportional elasticity. In some recent experiments I have 

 heated steam to a temperature that would have given all the power that 

 the highest steam is capable of exerting, which would have been 56,000 

 pounds to the square inch, if it had had its full quantum of water ; yet the 

 indicator showed a pressure of less than five atmospheres. Having satis- 

 fied myself, by repeated experiments, as to the certainty of this curious 

 fact, the thought struck me, that, if heated water were suddenly injected 

 into the superheated steam, the effect would instantly be the formation of 

 highly elastic steam ; the strength of which would depend upon the tem- 

 perature and quantity of the supercharged steam and of the water inject- 

 ed. To ascertain the truth of this theory, I made the following experi- 

 ments : 



A generator was filled with water and heated to about 500 degrees, and, 

 consequently, exerting a force of about 50 atmospheres ; but the pressure 

 valve being loaded to about 60 atmospheres, it prevented the water from 

 expanding into steam. The receiver, which was destitute of both water 

 and steam, was heated to about 1200 degrees : a small quantity of water 

 was injected into the generator with the forcing pump, which forced out 

 from under the pressure valve into the receiver a corresponding quantity 

 of heated water, and this instantly flashed into steam, which, from its 

 having ignited the hemp cord that covered the steam-pipe ten feet from 

 the generator, must have been at a temperature of at least 600 degrees, 

 which would be equal to about 800 atmospheres ; but from want of water 

 to give it its necessary density, the indicator showed a pressure of about 

 5 atmospheres. Whether the pressure of the steam, which was rushing 

 through the steam-pipe, was at 5 or 100, or more atmospheres, the steam- 

 pipe kept up at the high temperature before-mentioned, which I attri- 

 buted to the steam being supercharged with caloric. The pump was now 

 made to inject a much larger quantity of heated water, and the indicator 

 showed a pressure of from 50 to 80 atmospheres : it soon expanded, the 

 throttle valve being partly opened, to the former pressure of about 5 at- 

 mospheres. The water was then injected again and again, and the indica- 

 tor was observed to oscillate at each stroke of the pump from 5 to between 

 40 and 100 atmospheres, according to the quantity of water injected; 

 clearly showing that, at this reduced pressure, there was a great redundan- 

 cy of heat, with little elastic force. It soon occurred to me that to this 

 might be traced the true cause of the tremendous explosions that sud- 

 denly take place in low as well as high pressure boilers. 



There are many instances where, immediately before one of these ter- 

 rific explosions had taken place, the engine laboured ; showing evidently a 

 decrease of power in the engine. To illustrate the theory of sudden ex- 

 plosions, let us suppose the feed-pipe or pump to be choked ; in this case 

 the water would soon sink below some parts of the boiler, which should 

 be constantly covered by it, thus causing them to become heated to a much 



