AMF-RICAN INSTITUTE. 575 



If this extra capacity of the pump should be such as to enable 

 it to deliver two and a half cubic feet per hour for the power of 

 each horse, instead of the one and a quarter cubic foot required 

 to furnish the steam necessary for the engine, the depth of Water 

 in the boiler, if the pump should be kept constantly at work, 

 would be increased six inches per hour. 



A pump of the proportions assumed, .that is, one which would 

 send into the boiler such quantity of water that only one half 

 could be evaporated, and sent out again in the form of steam, 

 would if worked at the rate of twenty-five strokes per minute, 

 raise the surface of the water at the rate of ^-oVo" '^^ ^^ ^'^^'^ P^^ 

 stroke, or -j- of an inch per minute, or at about the same rate 

 that the extremity of the minute hand moves in a common sized 

 watch ; and the feed pipe is, or always ought to be attached to 

 the boiler in such situation that the entering current will not 

 ripple or disturb the surface. And here the question naturally 

 presents itself: can the introduction of cold water at such a rate 

 and under such circumstances be productive of additional dan- 

 ger ? It is believed that the answer must be decidedly in the 

 negative ; and that next to withdrawing or extinguishing the fire 

 and putting a stop to the introduction of steam, the safest course 

 to be pursued when a boiler becomes overheated, is to put in 

 requisition the whole power of the feeding. apparatus, and in that 

 way slowly and regularly cool down the overheated part. This 

 course is certainly, for a time, attended w'ith more danger than 

 the other, not because cold water is introduced for this lowers 

 the temperature of the whole mass and diminishes the rate at 

 which steam can be produced from it, but because the weakness 

 caused by the previous overheating continues until the slowly 

 rising water reaches and cools the weakened part, and thus res- 

 tores it to something near its original strength. Should a boiler 

 be overheated while the engine was at rest and the safety valve 

 closed, it would probably be attended with danger either to raise 

 the valve or start the engine, as the ebullition of the water 

 caused by either proceeding w^ould bring it suddenly into contact 

 with the heated metal and steam would be generated with dan- 

 gerous rapidity, but this differs from the case under consideralion. 



With regard to the opinion that a boiler cannot explode which 

 contains the proper quantity of water the writer offers no 

 remarks of his own, but refers the club to the report of the 

 "committee on explosions of the Franklin Institute." The con- 

 clusion at which they arrived, after concluding the most extensive 

 and reliable set of experiments yet made in the premises, will be 



