266 WILLIAM FIELD HOW. 
Iron for Bridge Work. 
With length of Plate. | Across the Plate. 
Stress per| Ultimate || Stress per| Ultimate 
sq. in. with-| Elongation |/sq.in. with-| Elongation 
outfracture| in 10”. outfracture| in 10”. 
Plates ... ose See ...| 22 tons | 10°/, || 18 toms) 
Angles, tees and flat bars ...) 23 tons Zhe 
Rivet and bolt iron ... .... 24 tons asp cips 
The iron plates and bars must also be capable of being bent 
cold, without signs of fracture, to an angle of forty-five degrees, 
the radius of the inner angle being not more than twice the thick- 
ness of the plate. The rivets must be capable of being bent 
double, when cold, without signs of fracture. 
Steel for Bridges. 
The steel for bridges must be manufactured by the open hearth 
process, and have an ultimate tensile strength of not less than 
thirty tons or more than thirty-three tons per square inch, with 
an elongation of at least twenty per cent. in eight inches. 
Strips cut lengthwise or crosswise, one and a-half inches wide, 
heated uniformly to alow cherry red, and cooled in water at 
eighty-two degrees Fahr. must stand bending in a press to a curve 
of which the inner radius is one and a-half times the thickness of 
the steel tested. 
Steel rivets must be capable of being bent double when cold, 
and also after having’ been heated to a low cherry red, and 
quenched in water, the water having a temperature of eighty-two 
degrees Fahr. 
Steel Plates for Bowlers. 
The steel plates for boiler shells are to be manufactured by the 
open hearth process from hematite ore, and must have an ultimate 
tensile strength of from twenty-six to twenty-nine tons per square 
inch, with an elongation of not less than twenty-five per cent. in 
eight inches. 
Strips cut lengthwise and crosswise, one and a-half inches wide, 
must stand being bent in a press to a curve of which the inner 
