PROCEEDINGS 1841 — 1848. 
185 
At a meeting at Wakefield, held iu July, 1842, Mr. Henry 
Hartop read a paper, on the relative properties of Iron made by the 
use of cold and hot air blasts in the smelting furnace. In 1829 the 
use of hot air in the smelting furnace for the manufacture of cast 
iron was introduced at the Clyde Ironworks, near Glasgow, and at 
the fourth meeting of the British Association, held at Edinburgh in 
1834, Dr. Clarke gave an account of its success, and stated that 
whereas with the cold air blast eight tons of coal were required to 
make one ton of iron, with a heat of 300 degrees Fahrenheit five tons 
produced a ton of iron to which must be added 8 cwts. of coal for 
heating the iron. In 1833, the temperature of the air was increased 
to 600 degrees, and it was found that raw coal (coke having been 
previously used), might be used, which reduced the quantity of coal 
required to 2 tons 5 cwts. per ton of iron made. In the following 
year, Mr. Hartop, at a meeting of the Association at Dublin, stated 
that Dr. Clark was in error, and that five tons of coal with a cold 
blast would reduce one ton of iron, and that the amount with the 
hot blast was 2 tons 15 cwts., which caused a saving of 12s. 6d. per 
ton of pig iron. But against this there was a deterioration of value 
in the iron of 17s. 6d. per ton, and in the succeeding seven years the 
difference in the value had been increased to 32s. 6d. per ton. The 
iron made with the hot blast is inferior to that made with the cold 
blast in the following particulars : — Its greater weakness under impact, 
greater loss in re-melting, (amounting to 2 cwts. per ton), and the 
great irregularity in the contraction of castings when cooling. From 
these and other circumstances he considered it a debt due to the iron 
trade to call attention to it, and after reading his paper at the British 
Association at Dublin, its importance was at once recognised, and a 
sum of money appropriated for making needful experiments which 
were carried into execution by Mr. Fairbairn, the Engineer, of Man- 
chester. Mr. Fairbairn experienced a difficulty in ascertaining the 
composition of the irons experimented upon, in consequence of many 
of the manufacturers being unwilling to give information, but the 
result of his experiments went to prove the correctness of the views 
he had stated, and the strength of cold blast iron was in all instances 
greater than that manufactured with the hot blast, and the results 
Q 
