56 Hazard on the Explosion of Steam Boilers. 



to subside below any part of the boiler which is exposed to 

 the fire. In case the water should settle, it may be known 

 by having a tube, with its upper end trumpet-mouthed, and 

 its lower end fixed in the boiler, entering a few inches be- 

 low the surface of the water ; then as soon as it subsides 

 sufficiently to allow the steam to blow off, the blast will give 

 warning that no time should be lost in supplying the water 

 or checking the fire.* When highly surcharged steam is 

 rushing from the safety valve, or any other aperture, it may 

 be known by its perfect invisibility, even in the coldest day, 

 nor can it be seen at any distance from the valve or cock ; it 

 is however, condensible ; as may be seen by holding any cold 

 substance in its range. 



4. Facts and Observations, on the bursting of the boilers of 

 Steam Engines. By Erskine Hazard, Esq., Civil En- 

 gineer.] 



The frequency of disasters arising from the bursting of 

 boilers, in steam boats, both with high, and low pressure en- 

 gines, makes it the imperious duty of all those who have 

 given particular attention to the subject, to make public any 

 ideas which may throw light on the cause of them, as they 

 may thereby aid in preventing repetition. With this view, I 

 take the liberty of sending you the following explanation, 

 which was given to me by our countryman Perkins. He 

 builds his theory, on the ground that the power of steam does 

 not depend upon temperature alone, but principally upon the 

 quantity of water that is contained in a given bulk of it ; in 

 other words that its power is derived from its compression. This 

 corresponds with the experience of the late Col. Alexander An- 



* This will apply only to low pressure boilers, on account of the 

 height of the columa which would be required to balance the pressure 

 of the steam. The high pressure engine as used, in Cornwall, would 

 require a column, varying from 60 to 120 feet ; and the new high pres- 

 sure safety engine, now coming before the public , would require a 

 column more than four times as high as St. Paul's cross, to balance the 

 steam. 



f This communication from Mr. Hazard, was received a month ear- 

 lier, than that from Mr. Perkins, although too late for insertion in our 

 number for May. The facts and reasoning which it contains, are inten- 

 ded to enforce, and confirm, the theory offered by Mr. Perkins ; we, how- 

 ever, do not apprehend that our readers will object to some repetition, 

 on a subject so truly of vital importance — Ed. Franklin Journal. 



