NEW BOILER. 



the fire, more than five times greater than that of a boiler Boiler for gene- 

 rating steam ; 

 having its 

 bottom termi- 

 nating in tubes. 



of equal diameter, and of the ordinary form : how much "; aUn § steam 



» having its 



this difference must aft'ect the celerity of heating is easy to bottom termi 



In the manner in Avhich boilers are usually set, their 

 vertical sides are but little struck by the flame, and on that 

 account, I have not taken the effect of the sides into con- 

 sideration in my estimate; but even taking them into ac- 

 count, the new boiler will always have a surface exposed 

 to the fire, at least twice as great as that of a common cj- 

 lindrical boiler of the same diameter, as can easily be 

 shewn. 



The new boiler being twelve inches in diameter, and 

 twelve inches high, and each of its seven tubes being three 

 inches in diameter, and nine inches high, its surface is 

 1160.44 square inches, without reckoning the circular 

 plate that closes its top, nor its neck. 



The surface of the bottom and sides of a cylindrical 

 boiler of twelve inches in diameter, and twelve inches 

 high, will be 566.68 square inches. 



As the quantity of heat that enters a boiler in a given 

 time, is in proportion to the extent of surface that the 

 boiler presents to the fire, it is evident, that other circum- 

 stances being the same, a boiler with tubes descending from 

 its bottom, will be heated at least twice as soon as a cy- 

 lindrical boiler of the same diameter, with a flat bottom. 



In order that a cylindrical boiler with flat bottom, sur- 

 rounded by flame on all sides, might have the sarnie extent 

 of surface exposed to the fire as a boiler with tubes, it 

 would be necessary to give it a diameter greater than that 

 of the boiler with tubes in the proportion of the square 

 root of 1160.44, to the square root of 566.68, that is, of 

 17.171 to 12. 



Therefore, in order that a cylindrical boiler with a flat 

 bottom, might have the same extent of surface exposed to 

 the fire as our boiler with tubes, of twelve inches in dia- 

 meter, it would be necessary to give it a diameter of 

 17.171 inches. 



But if the diameter of a boiler intended for producing 

 Steam be increased, it is necessary, at the same time, to 

 Increase its thickness, in. order to increase its strength. 



The 



