210 Geology, Mineralogy, Scenery, &c. 
smoke formed a striking contrast with the spray and fog of 
the cataract. It might have been twenty-five or thirty feet 
in height, and ten or twelve in diameter. Vast bellows, ri- 
sing and falling alternately by the action of water, threw in 
torrents of air; at the bottom, while at the top, the workmen 
were almost constantly occupied in putting m the ore, with 
charcoal and limestone in successive layers and in mixture. 
The ore is previously roasted in the open air; it is broken 
into pieces of a proper size, arranged in layers alteraately 
with chareoal, and when the heap is three or four feet high 
the fire is kindled and allowed to burn slowly for many 
hours. ‘The cohesion of the cre is in this manner impair- 
ed——sulphur, arsenic and other volatile things are expelled, 
and it is prepared for the fiercer heat to which it is subject- 
ed in the furnace. This last is shaped somewhat like an 
egg—a section being removed from each end and the smal- 
ler end beig uppermost. At the top it is only four or five 
feet in diameter, and there is little appearance of the vehe- 
ment heat which exists below. The ore, which is here melt- 
ed is principally from the Salisbury bed, but partly alse 
from the adjoining state of New-York. Both kinds are ox- 
ids, as indeed are all the iron ores which are profitably and 
usefully wrought; only they are more or less mixed or com- 
bined with sulphur and arsenic and with silex or flinty earth, 
argil or clayey earth, and other earthy matters and with for- 
elgn metals ; ehront titanium, manganese, &c. The princi- 
pal steps in fine operation are ‘therefore easily explained on 
principle. The roasting has been already explained. In 
the furnace the charcoal, aided by the fierce heat, detaches 
the oxigen and flies away with it in the form of carbonic 
acid gas ; the limestone although by itself infusible, by uni- 
ting with the earths and sulphur and other foreign bodies, 
removes them, at the same time promoting the melting 
of the entire mass, and thus in the language of the furna- 
ces it actsasa flux. The iron also to a considerable ex- 
tent, combines with the carbon and thus becomes very flu- 
id, and capable of being cast into any desired form. At the 
bottom of the furnace, the slag or dross floating at the top of 
the melted iron, is occasionally raked off, and the iron is ei- 
ther allowed to run out at a tap-hole, or is ladled out with 
large iron ladles managed by hand, and thus poured into the 
moulds into which it is to be cast. ‘The slag or dross which 
