128 OF THE GENERATION AND [SECT. HI. 



the boiler, and would confine the cooler parts of its content to where the smoke 

 was of the lowest temperature. 



231. Smaller cylinders, or rather tubular boilers, have frequently been pro- 

 posed for generating steam ; Blakey's has already been mentioned, (art. 25.) and 

 Count Rumford had one put up at the Royal Institution, in 1796, for generating 

 steam for warming the rooms. His ideas on the application of his construction to 

 steam engine boilers are worthy of attention. 



232. Count Rumford's Boiler. The object of this boiler was to get a larger 

 quantity of surface, and the Count had a model of it made and presented to the 

 French Institute. (October, 1806.) This model, as far as it differs from an 

 ordinary steam boiler, being described, the reader will easily understand how to 

 apply it on the large scale. 



The body of the boiler is in the shape of a drum : it is a vertical cylinder of 

 copper, 12 inches in diameter and 12 inches high, closed at the top and bottom by 

 by circular plates. 



In the centre of the upper plate there is a cylindrical neck 6 inches in diameter, 

 and 3 inches high, shut at the top by a plate of copper, 3 inches in diameter and 

 3 lines in thickness, fastened down by screws. 



The flat circular bottom of the body of the boiler, which as before stated is 12 

 inches in diameter, being pierced by seven holes, each 3 inches in diameter, seven 

 cylindrical tubes of thin sheet copper, 3 inches in diameter and 9 inches long, 

 closed at the lower ends by circular plates, are fixed in these holes, and firmly 

 riveted, and then soldered to the flat bottom of the boiler. 



On opening the communication between the boiler and the supply cistern, the 

 water first fills the seven tubes, and then rises to the cylindrical body of the boiler ; 

 but it can never rise above six inches in the body of the boiler, for when it has got 

 to that height, the floater is lifted to the height necessary for shutting the cock 

 that admits the water. As the seven tubes that descend from the flat bottom of the 

 body of the boiler into the fire-place are surrounded on all sides by the flame, the 

 liquid contained in the boiler is heated, and made to boil in a short time, and with 

 the consumption of a relatively small quantity of fuel ; and when the vertical sides 

 of the body of the boiler, and its upper part, are suitably enveloped, in order to 

 prevent the loss of heat by these surfaces, this apparatus may be employed with 

 much advantage in all cases where it is required to boil water for procuring 

 steam. 



And in the case where the boiler is constructed on a great scale, the seven tubes 

 that descend from the bottom of the boiler into the fire may be made of cast iron, 

 whilst the body of the boiler is composed of sheet iron or sheet copper. 



But in all cases where it is required to produce a great quantity of steam, it will 



