Proceedings of tee P olytechxic Association. 1017 



troiiLle was. After miicli overhauling it was found that the indica- 

 tor was not properly attached. There are few of our master mechan- 

 ics who could take an indicator diagram properly. The indicator 

 will give the measure of the steam hut not the power of tlie engine. 

 Mr. Wilcox read the following paper on 



BABCOCK AND WILCOX'S TUBULOUS BOILEK. 



Mr. Stephen Wilcox drew upon the blackboard a design of the 

 steam tubulous boiler invented by Messrs. Babcock and Wilcox — an 

 engraving of which is given on the opposite page — and read the fol- 

 lowing paper, setting forth its advantages : 



This boiler is believed to combine those correct principles of con- 

 struction and operation which science and engineering experience 

 have established as essential to the highest efficiency, economy and 

 safety. It is neither a radical departure from established practice 

 nor a mere variation of form for the sake of novelty, but has been 

 designed with strict regard to the following recpiirements of a per- 

 fect'steam hoiJer : 



1st. It should be simple in construction, and be made of the best 

 materials sanctioned by use. 



2d. It should have a constant and thorough circulation of water 

 throughout the boiler, so as to maintain all parts at one temperature. 



3d. It should be provided with a mud-drum to receive all impuri- 

 ties deposited from the water, in a place removed from the action of 

 the lire. 



4th. It should be provided wnth a combustion chamber so arranged 

 that the combustion of the gases commenced in the furnace, may be 

 completed before their escape to the chimney. 



5th. The heating surface should be arranged as nearly as possi])le 

 at right angles to the current of heated gases, and so break up the 

 currents as to extract the entire available heat therefrom. 



6th. The boiler should iiave sufficient water surface for the disen- 

 gagement of the steam from the water, in order to prevent foaming. 



Tth. It should have a steam and water capacity of not less than 

 two cubic feet per horse-power, to prevent sudden fluctuation in pres- 

 sure or water level. 



8th. It should have a great excess of strength over any required 

 strain, and should be so coiistructed as not to be liable to be strained 

 by unequal expansion. 



9th. The water space sliould be divided into sections, so that when 



