On the Origin of the Blast Furnace. 405 



The charcoal blast furnace of the present age attained the 

 height of thirty feet, the diameter enlarged to eight or nine 

 feet at the boshes, and the whole capacity equal in some in- 

 stances to 900 or 1000 cubical feet. 



The first successful experiments for making pig-iron from 

 coke were of course performed in the pre-existing charcoal 

 furnaces of this size ; but experience soon found out, that the 

 less active affinity of the carbon of coke for iron and oxygen, 

 required that a longer exposure of the iron-making materials 

 in contact with each other was necessary, to produce profita- 

 ble results : this could only be done oeconomically by an in- 

 crease in the size of the furnace, and a longer cementation of 

 the ores, in consequence of their prolonged descent. Hence 

 arose blast fi.irnaces which include a capacity of two, three, 

 four, five and six thousand cubical feet : and of late years fur- 

 naces have been erected equal to 10,000 cubical feet, witliout 

 the maxunum effect having been decidedly obtained. 



But to revert to the age and locality of the blast furnace, 

 with a view to determine the time of its introduction. Whether 

 it is a native discovery, (which I am rather inclined to believe,) 

 or was imported from other countries, I have not been able to 

 determine. The art of making castings from iron possesses 

 no great antiquity in this or any other country; it was un- 

 known, or at least not described, by Agricola in the sixteentli 

 century, who seems to have drawn and described every thing 

 then known of metallurgy; and we possess no traces of the art 

 earlier than the reign of Queen Elizabeth. 



I have examined the sites of many old charcoal blast fur- 

 naces, with a view of determining their age, by the quantity of 

 slags by which they were surrounded. Here, however, another 

 difficulty has been i)i every case but one interposed. The 

 manufacture of black bottles has, I think, been traced as far 

 back as the fifteenth century. At what time the manufacture 

 was introduced into this country, I am uncertain; but it is not 

 improbable that in early times, as in the last century, the slags 

 or cinders of the charcoal blast furnace have entered uito the 

 composition of black bottles, and created a consumption of that 

 sort of waste which otlierwise would have remained in the vi- 

 cinity of the furnaces. Tiie superior cjuality of the Bristol 

 black bottles has been attributed to the immemorial use- of a 

 portion of the slags of the charcoal liirnaces Irom the neigh- 

 bourhood of Dean Forest. The consequence of this k)ng- 

 standing ))ractice luis been, to carry from the furnaces not only 

 the old slags but those currently made. In one instance only 

 have I ioiuid from this source data l()r calculation. Before 

 the civil commotions of tlie seventeentli century, the kings of 



Kiijilaiid 



