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

In Chapter VIII., Wooden Bridging, we have the expression

S = 4b d²
l;

and if b = 10

d = 12

and l = 20

S becomes

4 × 10 × 144
20 = 288.

In Chapter IX., Iron Bridges, we have

T = ph
2f√h² + 4f²;

and making p =	4000
h =	500
f =	80