208 APPENDIX. 



Double the capacity 292-8 



Subtract bottom surface GOO 



Divide by side surface 59 ) 232-8 (4 feet, one of the dimensions 



236 of the bottom. 



4 ) 60 (15 feet, the other dimension. 



N.B. It cannot be of much importance that the dimensions should be in the proportion of 

 4 to 15, so long as the quantity of bottom surface is 60 square feet. 



II. Cylindrical Boilers, with the fire applied externally. 



RULE. Let the capacity for water and for steam be added together, and also the quantities 

 of fire surface ; then divide twice the capacity by the quantity of fire surface, and the result 

 will be the diameter. (126.) 



Also 1-27 times the capacity divided by the square of the diameter will give the length. 



Example. Required the dimensions of a cylindrical boiler for a 12 horse power, the whole 

 capacity being 293 cubic feet. 



m , , , n . c f Bottom surface 5'0 



Table, page 124, for 4 r 



I Side surface 4'9 



9-9 

 Horse power 12 



Fire surface 118-8 or 119. 

 Capacity 293 



2 



Fire surface 119) 586 (5 feet, the diameter. 

 Capacity 293 

 1-27 



2051 

 586 

 293 



Square of diameter = 25 ) 372-11 ( 14-9 or 15 feet, the length. 



25 



122 

 100 



221 

 225 



4. To find the requisite thickness for a rectangular or cylindric boiler. 



RULE. Multiply the load in Its. per square inch on the safety valve, by the greatest 

 diagonal of the section of the boiler in inches, and divide the product by, 



