Hazard on the Explosion of Steam Boilers. 57 



Person, who gave me the same theory many years since, and 

 at the same time informed me, that when distilling by steam, 

 he uniformly found the quantity of liquor produced in a giv- 

 en time, to be in exact proportion to the pressure within his 

 still. He hence concluded, that atmospheric steam, confi- 

 ned in any vessel, in such a manner that it could not get an 

 additional supply of water, might be heated red hot, without 

 bursting the vessel, or increasing its power. Perkins states, 

 that he has completely realized this idea, in his experiments. 

 He also mentions a fact communicated to him by Mr. Will- 

 iams, principal manager of the Dublin and Liverpool steam 

 company which was this. The people on board the boat 

 were alarmed, while on their voyage, by the smell of pine 

 smoke, and concluded that the boat must be on fire ; but 

 upon searching, they found a piece of pine wood on the top 

 of one of the boilers, which was nearly burnt to a coal ; it 

 was in such a situation, that no fire could have communica- 

 ted with it, except through the top of the boiler. The en- 

 gine at the time, was working with the steam only a 

 few pounds above the atmospheric pressure. Upon mention- 

 ing this circumstance to the captain of one of our Delaware 

 steam boats, he informed me, that the leaden joints of his 

 steam pipe were once melted, when the steam guage in- 

 dicated only the pressure at which they usually worked. In 

 both these cases, the water was so low in the boilers, that 

 the heat was communicated to the steam through a portion 

 of the boiler which had no water in contact with it, and 

 which of course became red hot, while the steam could not 

 part with its heat, downwards, to the water. 



The repellent power of heat, is the proximate cause of 

 explosion, according to Perkins' theory. This was one of 

 the principle obstacles he met with in the progress of his 

 experiments on high steam. In his tubular generators, he 

 found it impossible to keep the water in contact with the 

 metal, when a great heat was applied, until he adopted the 

 expedient of the pressure valve, loaded with five atmospheres 

 more than the pressure of the steam. The water was, as it 

 were wire-drawn, or passed through the centre of the tubes 

 iii a fine thread, being repelled by the heat of the sides, 

 which increased to redness, and finally destroyed the tubes. 

 To show this repellent power of heat, he made a hole of 

 one-fourth of an inch diameter in one of his generators, and 

 adapted a plug to it, which was removed when that part of 



Vol. XIIL— No. 1. 8 



