Cast Iron expands 1/162000 of its length for one degree of heat; greatest change in the shade, in this climate 1/1170 of its length; exposed to the sun's rays, 1/1000; shrinks in cooling from 1/85 to 1/98 of its length; is crushed by a force of 93.000 lbs. upon a square inch; will bear, without permanent alteration, 15.300 lbs. upon a square inch, and an extension of 1 1200 of its length. Weight of modulus of elasticity for a base of an inch square, 18,400,000 lbs.; height of modulus of elasticity, 5,750,000 feet.

Wrought Iron expands 1/143000 of its length for one degree of heat; will bear, on a square inch, without permanent alteration, 17,800 lbs., and an extension in length of 1 1400; cohesive force is diminished 1/3000 by an increase of one degree of heat. Weight of modulus of elasticity for a base of an inch square, 24,920,000 lbs.; height of modulus of elasticity 7,550,000 feet.