of Water in Steam-boilers. 



285 



antly followed by the foreman, in whose somewhat jeering looks 

 I could plainly read that he entertained but a poor idea of our 

 pluck. 



In addition to this, I may say that in " waggon boilers," a 

 shape than which none can be more unsafe, but which is now for- 

 tunately much less in use than in former years, bulging bumps 

 are very often observed, which are certainly due to the pressure 

 of the steam in the boiler upon the iron plates of the bottom, 

 when by extravagant or incautious firing they have been made 

 red-hot. Frequently, however, instead of bulgings or bumps 

 being thus produced, a disruption of the boiler takes place, 

 attended with more or less fatal consequences. Many such 

 accidents have thus happened at Manchester, and particularly 

 on Monday mornings. 



Tlie following occurrence, related to me by my friend Mr. A. 

 M. Perkins as having taken place in his presence in a boiler of a 

 pecidiar construction in which steam was generated by means of 

 his hot-water pipes, is also well worth mentioning, as I think 

 we may gather from it a correct explanation of the facts under 

 consideration; and the rough sketch below, which represents a 

 cross section of the boiler, will pei'haps explain the matter better 

 than I could do by writing. 



The boiler had the dimen- 

 sions indicated, and was 8 

 feet in length; it was filled 

 •with water to about A as 

 usual, the safety-valve had an j. 

 area of 4 inches. From such 

 a boiler the whole of the water 

 was completely driven ofi" 

 through the valve by vio- 

 lent priming ; that is to say, 

 steam was generated so fast 

 by a hot water pipe in the 

 limb B, that it completely 

 lifted up the water and vio- 

 lently squirted it out of the 

 boiler, as just related. In 

 such a case, the water being 

 heated by pipes, and not by 

 contact with the heated sur- 

 faces of the boiler, no other 

 mischief could result than 

 that of priming : but sup- 

 pose, on the contrary, such a 

 boiler to have been heated in 



