86 
At 120° all the bars stood two 5ft. blows and one 7ft. blow. 
At 26° only one bar stood two 5-feet blows, three broke 
at the second 5-feet blow, and one at the first 5-feet blow. 
At 60° all would probably have passed the test easily, 
many thousands having previously done so from the same lot. 
It will therefore be seen that the results are in perfect 
agreement in all these experiments, showing that bar iron, 
boiler plates, wire billets, and rails are most materially 
weakened by the action of intense cold, losing all their 
toughness, becoming quite brittle under sudden impact, 
and having their structures changed from fibrous to crystal- 
line. 
Similar instances could be given in illustration of this in 
the daily practice of engineering. In large works the break- 
ages of wrought iron are very considerable during frosts. 
Quarrymen find that their chains are very liable to fracture 
from the same cause ; and doubtless the numerous accidents 
of failing tires in our railways may be attributable to it. 
In many cases however the contraction of iron must also be 
taken into account, as it is a serious item. 
In conclusion, I think it cannot be doubted, after the 
above recital, that iron does become very much weaker, 
both in its cast and wrought state, under the influence of 
low temperatures. This subject is one of such paramount 
importance, that a careful series of investigations ought to 
be undertaken by one of our scientific bodies, to ascertain 
the precise nature of the changes which are thus shown to 
take place, as there is herein an item which materially 
affects the stability of all iron structures during frosty 
weather, and which has not hitherto been adequately 
recognised. 
“ On the Properties of Iron and Steel as applied to the 
Rolling Stock of Railways,” by Sir William Fairbairn, 
Bart., LL.D., F.R.S., &c. 
