Page:Transactions of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne 1838 Vol.2.djvu/164

154 At Plate I., Fig. 1, is a perspective view of the Roasting Furnace. Its bed or bottom, inside, upon which the charge of ore is spread to receive the action of the fire, is usually about six feet square, quite flat and formed of fire bricks, set upright upon their ends, and in contact. The fire-place is 3 feet 4 inches long, by 1 foot 4 inches broad, which, with the roof and sides, is formed of fire-bricks, enclosed by solid masonry, and strongly bound together by iron bars. The tease-hole, through which coals are supplied to the fire, is not represented in the figure, being, in this case, on the opposite side of the furnace. Three doors are usually formed on each side when convenience admits of it, through which, and an end door b, the ore can be turned and raked backwards and forwards; the middle door a in front, is made larger than the óthers, for the purpose of more easily introducing and withdrawing the charge of ore. Immediately below this door is a trough c, 18 inches deep, 2 feet wide, and 4 feet long, filled with water, into which the ore is suffered to fall red hot when raked out of the furnace; and directly above this door is a wide-mouthed sheet-iron tube, d, communicating with the chimney, through which the unwholesome effluvia of the ore is conducted away, without injuring the workmen, during the operation of withdrawing the charge. A moveable iron screen e is at the same time placed over the trough, against the side of the furnace, within which the ore falls, effectually preventing the escape of noxious vapour.

Although the construction and size of the roasting furnaces, at most of the smelting mills in this district, are nearly alike, yet considerable difference is found in the rate and mode of working them. At some places, two men manage a furnace, into which one bing of ore is put at a charge, and the furnace is charged and drawn five times in eight hours. Each pair of men work 8 eight-hours-shifts per week, and are relieved at the end of each shift by another couple, who work with them alternately eight hours on and eight off; in this manner roasting eighty bings of ore per week in one furnace.

At other places three charges, making together four bings of ore, are worked in eight hours by one man; and three men, working each six shifts per week, roast in one furnace seventy-two bings of ore; and,