COMPOSITION OF CAST IRON. 117 
On the difference between the Composition of Cast Iron pro-~ 
duced by the Cold and the Hot Blast. By Tuomas Tuomson, 
M.D., F.R.S., L.& E., &c., Professor of Chemistry, Glas- 
gow. 
Ar the meeting of the Association last year in Bristol, consider- 
able difference of opinion was entertained respecting; the ad- 
_ yantages said to be obtained by heating the air. before it is in- 
troduced into the furnaces in which iron is smelted, and it, was 
finally admitted by all parties that the only unexceptionable 
mode of determining the question would be to institute a set of 
experiments to determine the relative qualities of hot and cold 
blast iron, and to make a comparative set of analyses of each 
sort in order to determine whether any, and what, differences 
exist in their chemical composition... Messrs. Hodgkinson 
and Fairbairn, of Manchester, undertook to make a compara- 
tive set of experiments on each sort, and Mr, Fairbairn stated 
the result of their experiments in the mechanical section of the 
Association. A committee was appointed by the chemical sec- 
| tion to investigate the chemical composition of hot and cold 
blast iron. I had the honour of being named one of the mem- 
_ bers of that committee. I have accordingly made a certain 
-number of analyses, and my object in this paper is to state the 
_ results which I have obtained.. I do not know what has been 
_ done by the other members of the committee ; I was at too 
_ great a distance from all of them to enable us to operate to- 
gether; I therefore take it for granted that the object in view, 
when individuals living at such distances from each other were 
_ named together, was that each individual should make experi- 
_ ments on the.iron made in his neighbourhood; and that the 
section, by comparing together all the results, might have it in 
_ their power to come to a proper conclusion respecting this most 
portant subject. ) 
__ A great deal of cast iron, and a considerable quantity of bar 
_ iron is now made in the neighbourhood of Glasgow. Probably 
_ the amount last year was not far short of 200,000 tons. It is 
| well known that Glasgow is surrounded by one of the richest 
_¢oal-fields in Britain. The coal is not only abundant, but of 
excellent quality, and the iron ore fortunately exists in great 
abundance, stratified or in nodules in the coal measures. The 
Ore is always a carbonate of iron, never absolutely pure, and 
_ Varying considerably in this respect even when we examine dif- 
