84. Rule II. - To ascertain the load that would fracture a beam of wood strained in the direction of the length - Multiply the area of the least cross section of the piece in inches by the weight that will tear asunder a bar an inch square of the same material - Tables II., III., and IV. - and the product will be the weight in pounds. The load upon a square inch should never exceed one-fourth of that which would cause rupture, and in many cases it should be less - see Art. 78.