SECT, in.] CONDENSATION OF STEAM. 127 



it shall be capable of converting 7 cubic feet of water into steam per hour, at a 

 pressure of 4 atmospheres. 



A boiler for this purpose should contain about 9 cubic feet of space for each 

 cubic foot of water boiled off per hour ; consequently, its whole content will be 63 

 cubic feet. The surface for the fire should be 7 x (4-9 + 4) = 62'3 feet, (see art. 

 204.) Therefore 



?J1|? = 2-02 feet, the diameter. 



' 



And 



1-27 x 63 ,. 



2-02 x 2-02 = 20 feet ' the 



Example II. Let the boiler be required to boil off 24 cubic feet of steam per 

 hour, at 3 atmospheres, with 11 feet of space in the boiler for each cubic foot 

 boiled off. 



The content = 11 x 24 = 264 feet. The surface 24 x (4-6 + 4) = 206-4 feet ; 

 therefore 



n v 2R4 



* = 2-6 feet nearly, the diameter. 

 206-4 J 



And 



1^?64 =50 feet nearly; 



but two boilers each 25 feet long would be better. 



Example III. If a low pressure steam boiler be made cylindrical for a 12 horse 

 power, under the same conditions as a rectangular one, (art. 225.) 



Then the content = 12 x 2 x 12-2 = 292-8 feet. And the surface =12(5 + 4-9) 

 = 118-8 feet; therefore, 



2 x 292-8 



= 5 feet nearly, the diameter ; 



118-8 



, 1-27 x" 292-8 

 5x5 



The boiler should therefore be 14-8 feet long, and 5 feet in diameter, and this 

 I think a better form for boilers than the usual rectangular ones. See Plate n. 



230. The steam pipe S should lead from immediately over the fire, and the 

 water should be admitted at the opposite end at N ; and in order that the 

 sediment may be with more certainty deposited where the fire has least force, I 

 would insert a partition O across the boiler, to rise within about four or five 

 inches of the surface of the water. This would prevent cold water checking the 

 steam, and also cause the deposit of sediment to take place where the water entered 



