This section is from the book "The Tinman's Manual And Builder's And Mechanic's Handbook", by Isaac Ridler Butt. Also available from Amazon: The Tinman's Manual And Builder's And Mechanic's Handbook.
How many superficial feet arc contained in a boiler 23 feet in length and 5 ½ feet in width ?
Set 1 on b to 23 on A; and against 5.5 upon b is 126.5 square feet upon a. If 5 square feet of boiler surface be sufficient for each horse-power, how many horses' power of engine is the boiler equal to ?
Set upon b to 126.5 upon a; and against 1 upon B is 25.5 upon A.