From Transverse Strains, Art. 702, we have -

d3=(82+yd)l3/0.576F, which may be modified so as to take this form:

(64.)

which is a rule for the depth or thickness of solid timber floors for dwellings, assembly-rooms, or office buildings, and in which y and h are constants depending upon the material; thus, for -

 Georgia Pine............................ y = 4, and h = 0.314 Spruce........................................ y = 2 1/2 ,, h = 0.365 White Pine.................. y = 2 1/3 ,, h = 0.389 Hemlock......................................................... y = 2, ,, h = 0.39

The rule may be stated in words thus:

Rule XLVII. - Multiply the length by the value of y, and by the value of h, as above given; to the product add 82; multiply the sum by the cube of the length; divide this product by 0.576 times the value of F, in Table III.; then the cube root of the quotient will be the required depth in inches.

Example. - What depth is required for a solid Georgia-pine floor to cover a span of 20 feet? For Georgia pine F= 5900; y, as above given, equals 4, and h equals 0.314; therefore, by the rule -

or, the depth required is, say, 6.32 or 6 5/16 inches.