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

159. The tensile strength of wrought iron assumed as 1,000.

Material.	Tension.	Compression.	Cross Strain.	Sum.	Weight per cubic ft.	Sum divided by weight per cub. ft.
Cast-Iron	300	1,666	31.68	1,997.68	450	4.4
Wrought Iron	1,000	733	55.40	1,788.40	480	3.7
Wood	133	66	5.60	204.60	30	6.8

The advantage possessed by iron over wood, is in durability only. The above figures show how much more of the strength of the material is consumed by its own weight in iron than in wood. In actual practice, however, the method of making joints and other details often render iron the lightest material.

RULES FOR PRACTICE.

TENSION.

160. The tensile strength of any material, is expressed by the formula

T = Sa,

Where T represents the whole strength,

S represents the strength per square inch,

a represents the area of section in inches.