25 



They must be true to form and dimensions, of a work- 

 manlike finish and free from injurious blowholes and 

 defects. All castings must be annealed. 



When tested in specimens of uniform sectional area of at 

 least square inch for a distance of 2 inches, they must 

 show an ultimate strength of not less than 67,000 pounds 

 per square inch, an elastic limit of one-half the ultimate, 

 and an elongation in 2 inches of not less than 10 per cent. 



The metal must be uniform in character, free from hard 

 or soft spots, and be capable of being properly tool finished. 



CAST IRON. 



151. Except where cast steel or chilled iron is required, ot iron, 

 all castings must be of tough, gray iron, free from cold 

 shuts or injurious blowholes, true to form and thickness, 



and of a workmanlike finish. Sample pieces. I inch square, 

 cast from the same heat of metal in sand moulds, shall be 

 capable of sustaining, on a clear span of 12 inches, a central 

 load of 2,400 pounds, when tested in the rough bar. A blow 

 from a hammer shall produce an indentation on a rectangu- 

 lar edge of the casting without flaking the metal. 



TIMBER. 



152. The timber shall be strictly first-class 



southern yellow pine or white oak bridge timber, sawed 

 true, and out of wind, full size, free from wind shakes, 

 large or loose knots, decayed or sap wood, worm holes, 

 or other defects impairing its strength or durability. It 

 will be subject to the inspection and acceptance of the 

 Engineer. 



INSPECTION. 



153. All facilities for inspection of the materials and i 

 workmanship shall be furnished by the contractor. He 

 shall furnish without charge such specimens (prepared) of 

 the several kinds of steel to be used, as may be required to 

 determine their character. 



