Web, 1 1/2 inches thick.

The simplest bridge, consisting of a single stick, to span openings of
20 feet and under, is calculated according to the formula

------
/ 4WL
d = / ------ --
\/ 5000 b


[TeX: $d = \sqrt{\frac{4 WL}{5000 b}}$]

_Example._--The depth of a beam, of 12 feet span and 12
feet wide, to support a load of 22400 lbs. will be

------ --------------------
/ 4WL / 4 X 22400 x 12 x 12 -------
d = / ------ = / ------------------- = / 215.04 = 15 in. nearly
\/ 5000 b \/ 5000 x 12 \/


[TeX: $d = \sqrt\frac{4 WL}{5000 b}} = \sqrt\frac{4 \times 22400
\times 12 \times 12}{5000 \times 12} = \sqrt{215.04} = 15$]

The following Table was calculated by the above rule--and the
dimensions altered according to the actual practice of the writer.

Span. Breadth. Depth.