On Ihc Origin of ihc Blast Furnace. 103 



naturally be directed to every known state of iron, to prove its 

 capacity for resisting the violence of the necessary explosion : 

 and as ceconomy seldom enters into the views of the warrior, 

 quantity, more than the cost of production, would be the first 

 object of consideration when experiment had determined the 

 superior strength of carbonated cast iron, and its capability of 

 being run or cast into form. The malleable iron artillery with 

 its numerous hoops and cases would be abandoned, and the 

 strongest sorts of cast iron sought after. Demand would sti- 

 mulate the exertions of the iron-maker, who in time might be 

 led to reason that a larger furnace might produce a larger 

 quantity of iron. The old bloomery furnace would be en- 

 larged: and as every addition to the size, by increasing the 

 period of cementation and contact of the ores with the fuel, 

 would not only increase the fusibility and strength of the iron 

 b}' additional carbonation, but also materially i-educe the cost 

 of production, — a permanently enlarged furnace would be the 

 consequence, though still possessing the form and pi'oportions 

 of the bloomery furnace. A decided advantage having been 

 obtained by the enlargement of die furnace, in producing gray 

 or fusible cast iron, it is jirobable this improvement would be 

 pushed to the extreme ; and long before any adequate improve- 

 ment took place in the blowing machine, the soft and very 

 limited quantity of blast that was found sufficient to penetrate 

 a column of iron-making materials in the blast bloomery, 

 three or four feet high, would be found of difficult ascent 

 through a furnace of three or four times that height. The 

 combustion would in consequence proceed languidly, the in- 

 creased height and greater pressure of the ores would repress 

 the blast as it entered the twyre, and a period of difficulty and 

 distress be likely to ensue. In such an emergency as this, a 

 suspending medium was probably first thought oij and intro- 

 duced into the blast furnace; to which, at the time or since, 

 lias been given the name ol" boshes: these, by creating imme- 

 diately above the twyre a lateral suspension of the entire co- 

 lumn of smelling materials, removed the pressure from the 

 central parts (jf the furnace, ami allowed the blast to ascend 

 with more freedom and effect. Whatever benefit was derived 

 from the introduction of boshes into the earliest blast furnaces, 

 it would soon be found, that although by their means (juality of 

 iron and regularity of process v.cre obtained; yet (juantity, 

 which alone can yield profit, still depended upon some other 

 cause. This evil would be partially remedied by the increase 

 of the size or number of the bellows in those times, chiefiy 

 urged by the labour of man or the strength of cattle: but this 

 would intreu'sc liie jmniber of labourers, the value of (lie. 

 3 E 'J ojierativc 



