NEW BOILER. 



Bpjlerfor gene- c f the boiler into the fire may be made of cast iron, whilst 

 having its ' * ne body of the boiler is composed of sheet iron, or sheet 

 bottom ter- copper; it is certain that a boiler of this kind, sufficiently 

 tubes" 8 "* l ar g e f° r a steam engine, a dying house, or a spirit dis- 

 tillery, would cost much less than a boiler of the usual 

 form, of equal surface and power. 



But in all cases where it is required to produce a great 

 quantity of steam, it will be always preferable to employ 

 several boilers of a midling size, placed beside each other, 

 and heated each by a separate fire, instead of using one 

 large boiler heated by one fire. 



I have shewn, in my sixth essay, on the management of 

 fire, and the ceconomy of fuel, that beyond a certaiu limit, 

 there is no advantage derived from augmenting the capacity 

 of a boiler. 



It will be perceived, that the boiler which I have the 

 honour of presenting to this Society, is of a form fit for 

 being placed in a portative furnace, and it was actually in- 

 tended for that purpose. 



Its furnace, which is made of bricks, with a circular 

 iron grate of six inches in diameter, is built in the inside 

 of a cylinder of sheet iron, seventeen inches in diameter, 

 and three feet high, and can be easily transported from 

 place to place, by two men. 



This cylinder of sheet iron, which is divided into two 

 parts, in order to facilitate the construction of the masonry, 

 'weighs only forty-six pounds. The masonry weighs about 

 a hundred and fifty pounds, and the boiler twenty-twq 

 pounds. 



In order to form an estimate of the advantage which the 

 particular form of this boiler gives it in accelerating its 

 heating, We may compare the extent of surface that \t pre, 

 sents to the action of the fire, with that of the fiat bottom 

 pf a common boiler. 



The diameter of the bottom of a cylindrical boiler being 

 twelve inches, the surface is 113.88 square inches; but 

 the surface of the sides of the seven tubes that descend 

 from the flat bottom of our boiler (which is likewise twelve 

 inches in diameter) is 593.76 square inches. Therefore, 

 the new boiler has a surface exposed to the direct action of, 



the 



