— 79 — 
Pins, bored pin-holes, and turned friction rollers shall bo coated 
with wliifce lead and tallow before being shipped from the shop. 
All wrought iron must be tough, fibrous, anti unifonn in Quality of Material.* 
character. It shall have a limit of elasticity of not less than 20,000 
pounds per square inch. 
Finished bars mast be thoroughly welded during the rolling, 
be freo from injurious seams, blisters, buckles, cinder spots, or 
iniperfect edges. 
For all tension members double rolled bars must be used. They 
shall stand the following tests : 
Full sized pieces of flat, round, or square iron, not over 4^ 
inches in sectional area, shall have an ultimate strength of 50,000 
pounds per square inch, and stretch 12^ per cent, in their whole 
length. 
Bars of a larger sectional area than 4^ square inches, w r lien 
tested in tlie usual way, will be allowed a reduction of 1,000 pounds 
l)ei’ square inch for each additional square inch of section, down to a 
minimum of 46,000 pounds per square inch. 
When tested in specimens of uniform sectional area of at least 
i square inch for a distance of 10 inches, taken from tension memb- 
ers which have been rolled to a section not more than 4^ square 
inches, the iron shall sliow an ultimate strength of 52,000 pounds 
P er square inch, and stretch 18 per cent, in a distance of 8 inches. 
Specimens taken from bars of a larger cross section than 4 J 
inches will be allowed a reduction of 500 pounds for each additional 
square iucli of section, clown to a minimum of 50,000 pounds. 
The samo sized specimens taken from Angle and other shaped 
^ rou shall have an ultimate strength of 50,000 pounds per square 
inch, and elongate 15 per cent, in 8 inches. 
The same sized specimens taken from Plates less than 24 inches 
ln width shall have an ultimate strength of 48,000 pounds, and 
elongate 15 per cent, in 8 inches. 
The same sized specimens taken from plates exceeding 24 inches 
in width shall have an ultimate strength of 46,000 pounds, and 
elongate 10 per cent. 
All iron for tension members must bend cold, for about 90 
degrees, to a curve whose diameter is not over twice tlio thickness 
of the piece, without cracking. At least one sample in three must 
beiul 180 degrees to this curve without cracking. When nicked on 
one side, and bent by a blow from a sledge, tlie fracture must be 
nearly all fibrous, showing but few crystalline specks. 
Specimens from angle, plate and shaped iron must stand bend- 
From the specifications of Theodore Cooper. Esq., C.E. 
