From these tables the compressions follow more closely the generally received law than the extensions, and they may be regarded as fairly supporting the theory. The following results are found from experiments on wrought iron :

In 20 readings under loads from 0·56 tons to 11.26 tons per sectional square inch, the ratio of the weight to the extension varies from 219,459 to 242,665, the next highest being 234,982, so that the first is probably exceptional; the mean is 230,760. Here, then, the extensions are tolerably regular.

In the experiments on the cast-iron bars, the rods in compression were cased to prevent deflection. The modulus of elasticity will be seen to have varied in extension from 14,050,320 lbs. to 12,377,040 lbs., the mean of these two being 13,213,680 lbs.; in compression from 13,214,400 lbs. to 12,013,680, of which the mean is 12,614,040 lbs.

The modulus of elasticity of wrought iron, corresponding to the mean ratio of weight to extension, as given above, is 27,691,200 lbs.

TABLE No. 1.

ULTIMATE TENSILE RESISTANCE OF TIMBER IN LBS. PER SQUARE

ULTIMATE RESISTANCE OF TIMBER TO CRUSHING IN LBS. PER

TABLE No. 3.

TRANSVERSE RESISTANCE OF TIMBER.

E, modulus of elasticity; S, ultimate moment of resistance in

TABLE No. 5.

ULTIMATE RESISTANCE OF VARIOUS CAST IRONS IN TONS PER
SQUARE INCH OF SECTION.

ULTIMATE RESISTANCE OF VARIOUS BUILDING MATERIALS TO CRUSHING

FORCE IN LBS. PER SQUARE INCH OF SECTION.

MODULUS

TABLE No 7.

OF ELASTICITY AND LIMIT OF ELASTIC RESISTANCE OF VARIOUS MATERIALS IN LBS. PER SQUARE INCH OF SECTION.