6 



incurred, great defect in all machinery, &c. &c. so made; 

 4th, its unsoundness, when made into castings that require 

 to be turned, bored, or planed, &c.; on which occasions, if the 

 surface operated upon is not defective on its entire are 3^ a 

 defect so considerable will show itself, probably when nearly 

 finished, that both the casting and the great expense bestowed 

 upon it will be thrown away, and in many such cases the 

 expense of making the casting itself will be at least three 

 times greater than even the present great difference in the 

 value of the two kinds of iron. 



I need not unnecessarily occupy your time further than by 

 going more fully into the first of these points, — the great 

 weakness, under impact, of hot blast iron. 



My attention was first called to the subject by observing 

 great quantities of pig iron, on the wharfs at the iron foundries 

 and other places in this neighbourhood, very recently broken 

 into pieces so short as to prevent the labourer piling them in 

 cubical tiers in the usual manner; and on inquiry, I found 

 that they were so broken by loading and reloading, and that 

 they were made by the new process of using hot air in the 

 furnace, greatly miscalled an improvement in the manufacture 

 of cast iron. From these and other circumstances, I thought 

 it a duty due to the iron trade to call the attention of the 

 public to it, and having mentioned the subject at the meeting 

 of the British Association in Dublin, its importance was at 

 once recognised, and a sum of money appropriated for making 

 the needful experiments, which were carried into execution 

 by Mr. Fairbairn, the highly intelligent and indefatigable 

 engineer of Manchester. I was very sorry to find from his 

 report read at the Liverpool meeting, as well as from several 

 conversations which he had with me on the subject, that he had 

 experienced great difficulty in ascertaining the composition 

 of the irons experimented upon, in consequence of many of 

 the manufacturers being unwilling to give information ; and 



