86 Mr. Geobge Thomson on Blast Furnaces. 



Referring to the Table, the three first coals are found in the same 

 coal-field, and at no verj great depth from eacli other. The cold 

 blast results of these came directly under my own observation, and 

 are taken from several years work; the hot blast results are from a 

 neighbouring work, and subject to similar conditions in almost every 

 respect Here, then, in the same coal-field are three different coals, 

 wliich, when under similar conditions with cold blast give very 

 dififercnt results, so much so, as to have taken nearly twice as much of 

 one kind of coal to make a ton of iron as of another, (yard coal 5 J tons, 

 clod coal 3 tons); but when the hot blast is applied, we find they are 

 very nearly assimilated, so that, upon the coal which works best with cold 

 blast, that application has scarcely any effect, while on the inferior 

 coal it has a most surprising one. 



The two next coals in the table from the Wolverhampton coal-field 

 show a similar result. The sixth and seventh, or the two last coals 

 of table No 1, belong to North Staffordshire — the district of the 

 " Potteries." There my results are also given from a direct personal 

 observation of several years; and I do not think I err in saying, 

 that the materials of this district, taking coal and ironstone together, 

 are the worst in the kingdom for iron smelting. The coals given are 

 compared under precisely similar conditions both with cold and hot 

 blast, and although obtained from the working of a very small furnace, 

 (only 32 feet high,) the comparative results will not bo affected thereby. 

 They lie very close to each other, being merely separated by a 

 stratum of shale a few feet in thickness, often less, and, consequently, 

 show how great a difference occurs, not only in different districts, but 

 within a few yards, vertically, of the same field. 



With modifications of shape and increase of size, (to which we shall 

 attend more particularly under that head,) we were ultimately able to 

 work No. G, (ash coal,) in the furnace, without coking, and at a con- 

 sumption of only 21 tons to the ton of iron, with a make of upwards of 

 70 tons a week; but No. 7, (rider coal,) although these conditions 

 altered the make considerably and the yield slightly, wo were never 

 able to work without coking ; again and again we tried to do so by 

 commencing with a small quantity and gradually increasing it, but in 

 vain; every increase of this coal to the burden, without coking, was 

 followed by a decrease of yield, make, and quality. 



As regards ironstone, the effects of different qualities are not so 

 striking as those of coal, with respect to yield, but they have a great 

 influence on the quality of the iron produced. For instance, that 

 which is known as the Shropshire pennystone — a peculiar kind of 

 argillaceous ironstone found in small nodules imbedded in a stratum 

 of indurated clay — and containing about 30 to 35 per cent of iron, is 

 supposed to give the peculiar strength and toughness to the Shropshire 

 pig iron. When another ironstone, (siliceous,) locally termed " craw- 

 stone," which is found partially stratified in a bed of sandstone rock, 



