252 On the Origin and Discovert/ of Iron. 



introduce the furnace, about five-and-twenty years ago, for the 

 purpose of making bar-iron with coke and rich ironstones or 

 ores. The blast-bloomery he employed was 3 feet in height, 

 and from 2| to 2f feet in width ; hke the old charcoal bloomery, 

 it had an opening in front, and a blast-hole about nine inches 

 from the bottom which admitted a pipe of 1|^ inch in diameter. 

 The furnace was filled with coke, gradually heated, and the blast 

 introduced; then in small alternate portions were charged, 

 four cwt. of ironstone, and in the whole 10 bushels of coke, 

 containing about 700 pounds of fuel, or neax-ly the produce of 

 one ton of raw pit-coal. In less than one hour the whole 

 charge was smelted, the cinder was then tapped from the sur- 

 face of the iron, upon which the blast-pipe was now inclined 

 as in the old furnaces. After a period of six hours, the lump 

 was deemed sufficiently malleablized ; the front of the fur- 

 nace was broken down, and the mass carried to the Ibrge ham- 

 mer. In this way about 130 lbs of bar iron were obtained 

 from 4 cwt. of Lancashire ore, or the same quantity of roasted 

 ironstone of a very rich quality. 



The Lancashire ore contained about 290 lbs of iron; so of 

 this quantity 1 SOlbs only were recovered, or equal to 45 per cent, 

 of the iron, and about 30 instead of 65 from the ore. 



The ironstone was of a peculiar nature, a combination of 

 iron and bituminous matter; so that, when roasted, the dissipa- 

 tion of the inflammable matter left a pure oxide of iron in 

 thin beds or laminae, which in the crucible yielded upwards of 

 70 per cent.; so that not 40 per cent, of the iron only was 

 revived ; and if the yield in iron is deducted from the ironstone 

 in its raw state, two tons of which yielded about one ton of 

 iron, the produce was not more than 20 per cent. 



The whole operation, from filling to falling the furnace, took 

 eight hours. The bloom in drawing out lost about eighteen 

 pounds of iron ; so that at the conclusion of the experiment 

 not more than one hundred weight of finished bar-iron wa^ 

 obtained. A calculation founded upon this result, would give 

 for one ton of bar-iron twenty tons of raw coal, and five tons 

 of Lancashire ore ; or, when used in preference, ten tons of 

 ironstone, besides an immense increase of labour. 



To accidental enlargement of the blast-bloomery, we most 

 likely owe the discovery of cast-iron. With a view of im- 

 proving the process, some enterprising smith may have added 

 to the height of his furnace, and accidentally or by design en- 

 larged the dose of charcoal. In tapping the furnace previous 

 to refinement, he might be struck w ith a difference in the co- 

 lour of the scoria, and the increased fluidity of the iron which 



might 



