Handbook of Railroad Construction; For the use of American engineers. / Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States.

by George L. Vose

Let the span, or length, be 20 feet,

The breadth 12 inches, and depth 18,

required the load.

The formula

W = 5000bd²
4L

becomes

W = 5000 × 12 × 18²
4 × 240 = 20,250 lbs.

Again, the weight to be supported being 15,000 lbs., length 30 feet, breadth 16 inches, the formula for the depth becomes

d = √(15000 × 1440
5000 × 16) = √270 = 16 inches,

also,