RULES FOR CALCULATING THE STEAM ENGINE. 207 



Force in inches of mercury 120) 57681'Q (481 cubic feet, the volume of the steam 



480 from a cubic foot of water. 



968 

 960 



81 



RULE ii. To the temperature, in degrees, add 459, and multiply the sum by 38; divide 

 the product by the pressure in Its. per square inch. (84). 



Same Example. 

 Temperature 295 

 Add 459 



754 

 Multiply by 38 



6032 

 2262 



fts. per inch 59) 28652(486 cubic feet. 

 236 



505 

 472 



332 



BOILERS. 

 3. To find the dimensions of a boiler for a given power. 



I. Rectangular or Watt's Boiler, when it has no internal flues. 



RULE. The bottom surface should be about 5 feet for each horse power. (124). Take the 

 capacity of the boiler for water, and divide it by the quantity of bottom surface, and the 

 quotient will be the depth of water. 



Divide twice the capacity for water less the area of the bottom surface by the side 

 surface for fire and flue, and the result will be one of the dimensions of the bottom. Divide 

 the bottom surface by this dimension, and it gives the other. (125.) 



Example. To find the proportions of a boiler for an engine of 12 horse power, the capacity 

 for water being 12'2 cubic feet for each horse power. 



Horse power 12 Cubic feet per horse power 12'2 



Table, page 124, 5 Horse power 12 



Bottom surface 60 Capacity 146*4 



Horsepower 12 6,0) 14,6'4 capacity 



Table, page 124, 4-9 



Side surface 58'8 or 59. 



2'44 depth of water. 



