720 PROCEEDINGS OF SECTION J. 
specimen of which will not bear the prescribed compressive or 
tensile strain.” Now, with reference to this specification, I have 
to say that I have never tested, seen, or even heard of any kind 
of iron that would comply with it, and I do not believe that such 
a material has any existence. An English engineer of the highest 
eminence, whose opinion upon it I sought, replied as follows :— 
“There is one comfort about the specification you refer to giving 
1-625th extension for 20 tons, namely, that no such iron could 
have been manufactured, and therefore the bridges must have 
been built of something else; let us hope good Staffordshire 
iron.” What the bridges are made of I have no means of 
knowing ; but this I do know, that of all the iron I have tested, 
that which approached most nearly to this specification was hard, 
brittle, and utterly unsuited for the construction of works upon 
which the security of human life depends. All fairly good iron 
extends more than thirty times as much as this extraordinary 
specification permits. 
About four years ago the construction branch of the Railway 
Department gave up the preceding specification, and in lieu 
thereof required the metal to endure a tension of 20 tons per 
square inch, and to elongate at /east 7 per cent. Now, while the 
old specification excluded all iron known to me, this, by a strange 
contrast, includes almost all. I have never yet met with a 
specimen of bar-iron that would not carry 20 tons per square 
inch, and that did not elongate at least 7 per cent before 
fracturing, and only two of plate-iron, and one of these was cut 
from an exploded boiler of considerable age. The specification 
is, in fact, absurdly lenient, and consequently affords no real 
protection to the public. 
The earlier specifications of the New South Wales Railway 
Department were on the same lines as the first-mentioned 
Victorian specification, requiring a hard, unyielding iron, and 
expressly forbiddjng that quality of ductility which is now 
recognised by all competent authorities as being so highly 
desirable. At the Penrith Bridge, which was one of the earliest, 
test-pieces, two inches wide and half an inch thick, were to be 
cut from the plates, and when tested were not to stretch more 
than one-eighth of an inch in seven inches with 18 tons, quarter 
of an inch with 21 tons, half an inch with 23 tons, and three- 
quarters of an inch with 24 tons, and were not to break with less 
than 25 tons. (See Maw and Dredge, Road and Railway 
Bridges, p. 9.) Now, whether this specification was enforced or 
not I cannot say, but I think probably not, as plate-iron of 25 
tons, or 56,000 lbs. per square inch tenacity, is a thing I know 
of only by reading, and even that was accompanied by a ductility 
far above what this specification permits. Still, this test is not so 
utterly impracticable as the earlier Victorian one, as it permits at 
20 tons per square inch about twenty times as much elongation. 
