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Coal and Ore, stratum super stratum, until it be full; and so putting Fire to the bottom, they let it burn till the Coal be wasted, and then renew the Kilns with fresh Ore and Coal, in the same manner as before. This is done without Fusion of the Metal, and serves to consume the more drossy parts of the Ore, and to make it friable; supplying the Beating and Washing, which are used to other Metals.
From hence they carry it to their Furnaces, which are built of Brick or Stone, about 24 foot square on the outside, and near 30 foot in height. Within, not above 8 or 10 foot over, where it is widest, which is about the middle; the top and bottom having a narrower compass, much like the shape of an Egg, as in the Figure. See Fig. 4. A the Tunnel, C the Furnace, B the Mouth of the Furnace.
Behind the Furnace are placed two huge pair of Bellows, whose Noses meet at a little hole near the bottom. These are compressed together by certain Buttons, placed on the Axis of a very large Wheel, which is turn'd about by Water, in the manner of an Overshot-Mill. As soon as these Buttons are slid off, the Bellows are raised again by the counterpoise of weights; whereby they are made to play alternately, the one giving its blast all the time the other is rising.
At first, they till these Furnaces with Ore and Cynder intermixt with Fuel, which in these Works is always of Charcoal; laying them hollow at the bottom, that they may more easily take fire: But after they are once kindled, the Materials run together into a hard cake or lump, which is sustained by the fashion of the Furnace, and through this the Metal, as it melts, trickles down into the Receivers, which are placed at the bottom, where there is passage open, by which they take away the Scum and Dross, and let out the Metal as they see occasion.
Before the Mouth of the Furnace lies a great Bed of Sand, wherein they make Furrows of the fashion into which they desire to cast their Iron. Into these, when their Receivers are full, they let in their Metal; which is made so very fluid by the violence of the Fire, that it not only runs to a considerable distance; but stands afterwards boiling for a good while.
After these Furnaces are once at Work, they keep them constantly employed for many Months together, never suffering the Fire to slacken night nor day; but still supplyingthe
