Mb. Geouqe Thomson on Blast Furnaces. 



87 



is mixed with the pennjstone, even in proportion of 1 to 10, the 

 oflfoct is very observable in making tho iron much more fluid, although 

 it retains its stoutness. Again : the efifect of the " red ore " of Cum- 

 berland, or peroxide of iron, mixed with argillaceous, or other iron- 

 stone, is well known ; it adds in every case very materially to the 

 strength of the iron, and the effect is especially so with the hot blast. 

 Forge cinder, which is a protoxide of iron, mixed with siliceous or 

 other foreign matter, has a directly contrary effect both with cold and 

 hot blast. So much so, indeed, that I have seen hot blast iron 

 which had been made with a large proportion of " cinder " so weak as 

 to break into several pieces when dropped on the ground from tho 

 height of a couple of feet. I may hero remark, that it is not surprising 

 that we should hear so many conflicting opinions on the strength of hot 

 blast pigs, by those who only quote results without considering the 

 conditions which affect them. 



These results on the quality of iron by the use of different kinds of 

 ironstone, are very general, but such effects are well known and are 

 constant ; and when we consider that there is only one kind of iron, in 

 fact, surely it is worthy the attention of the scientific to inquire whence 

 arise such differences, and how they should be produced by a simple 

 mixture of " red ore," or of " forge cinder." 



2df Influence of shape and size. — We now come to a few results 

 connected with the shape of furnaces ; and on this point there seems 

 to be at different times a ruling fashion. At the time of making the 

 experiment to which I shall first refer, which was before the hot blast 

 had been brought into notice, the prevailing fashion in England was 

 to make the furnaces as narrow as possible, both at the " neck,** (or 

 filling place,) and at the *' hearth." The furnace on which the experi- 

 ment was made was at Lightmoor, in Shropshire, the shape and 

 size of which is represented fig. No. 1. It Fio. 1. 



worked worse than any of the others with the -VJ^J 



same coal, which was a mixture of those 

 already referred to in Table I; and the only 

 difference of its shape, compared with the 

 others, was in being about 6 to 9 inches 

 wider at the boshes, and 3 feet less in height 



This furnace consumed about 5 tons of 

 coals in producing a ton of iron, and made 

 only about 40 tons per week. The alteration 

 made upon it was very simple to appearance, 

 consisting only of widening the top from 3 feet, 

 to 5i feet diameter, and carrying that width 

 perpendicularly up 6 feet higher ; also placing 

 two filling holes, one on eacli side, over tweres, 

 instead of one in the middle, merely, as it 

 were, placing a cylinder of 5J feet diameter 



