high, and is re-enforced at the hearth with a steel jacket lb in. thick by 7 ft. high. Nos. 5 and 6 are furnished with 7-in. bronze tnyeres that extend into the furnace 1 ft. No. 7 has a telescope arrangement for the lily-ere, water-jacketed breast. and water-block, all the parts being made of bronze, and su easily adjusted that there is very little delay in replacing them when necessary to make repairs. Each furnace has four 31assick & Crooke hot-blast stoves, 22 ft. in diameter and 70 ft. high. They are arranged in a line just north of and parallel to the line of furnaces. Two of each of the four stoves are en wind " and two on gas," the change being made every half-hour in such a manner that there is a fresh stove " on wind " all the time. These stoves at present maintain an average temperature of only 1.250° F. to the hot-blast. Directly north of the line of stoves is the stock-yard. Dere the coke, ores, and flux are all handled. The coke is unloaded as needed from three rows of trestles placed parallel to the line of stoves, and back of these are three more trestles, from which the flux and ore can be unloaded when necessary. Usually the ore is unloaded directly from the boats on to the docks and taken to the hoists in barrows. It is handled at the docks by 13 Brown hoisting and conveying machines, having an aggregate capacity of 8,000 tons per 24 hours, A double hoist-tower and hoist-engine are placed between each second and third stove. They are the ordinary crane-hoists, and each cage. carries two barrows. The harbor was made by dredging, and is 2,000 ft, long by 150 ft. wide, with an average depth of 20 ft.
West, of the furnaces are the boiler and engine houses. The former is 1:47 ft. by 291 ft., and has 40 horizontal tubular boilers 6 ft. by 20 ft. The water used in these boilers and around the furnaces is pumped from the lake. The engine-house is 57 ft. by 250 ft. It is equipped with 10 Southwark blowing-engines, having steam-cylinders 40 in. by 60 in., and 6 cylinders 89 in. by 60 in, The valves are of the regular Porter-Allen link-motion, Two of these engines are held in reserve for contingencies, either one of which can be turned on to one furnace. In the pump-house are 8 compound duplex Worthington pumps, with steam cylinders 29 in, and itti in., water-cylinders 16 in, in diameter. and a stroke of 21 in. West of the engine-house is the main water-tank, which is 17 ft. deep and 40 ft. in diameter, and is supplied by means of three centrifugal pumps placed at the lake. In addition to the main tank there are four of smaller capacity, so placed as to be convenient to the furnaces which they are to supply.
The ores smelted by this plant are the hematites of the Lake Superior region. They may be roughly classified as hard and soft ores. In making the mixture, about 15 per cent of the former to $5 per cent of the latter is mixed with a dolomite for the flux, and coke for the fuel. The richest ore will analyze about 62 per cent of Fe (iron), and the poorest will not fall below 50 per cent of Fe. They show on an average about 1.80 per cent of Sills (silica), .021 per cent of S (sulphur), and .69 per cent of P (phosphorus). The dolomite contains 1 per Cent of 1 per cent of (alumina), 53 per cent of and -1:5 per cent of (magnesium carbonate).
These furnaces are built to make 300 tons of pig-inm each per day. The iron is run from the furnaces into ladles of 12 tons' capacity each, and taken by locomotives to the steel-mill in the liquid state. The cinder is carried off by Weiner cindei'-buokets and dumped into the lake before it has time to harden.
The (his-regulating and C'wl-off Ira Kennedy, of Sharpslairg, manager of the Isabella furnaces, has designed it gas-regulating. and cut-oir valve which has been found a very eotivt.niunt arrangement, since one furnace luny be cot off without stopping the others. In a furnace-plant which comprises several furnaces, it has been found conducive to the regularity of work to cause the gas from all the furnaces to discharge into one main flue, from which the boilers and stoves are supplied. Valves have been placed in the main flue. in order to be able to cut it off from an individual furnace, so that the men can get access to parts where the presence of gas would be dangerous. Owing to the large size of the flues and the necessarily large dimensions of the valves, it has been found difficult to shut off the gas perfectly. Mr. Kennedy, instead of making the flue continuous, divides it by cross-walls into parts corresponding to the number of furnaces, and connects the adjacent parts with each other by removable pipe-connections. The construction of the device is shown in Fig. 2. The U-shaped pipe shown is attached to a plate-casting having holes registering with the openings of the pipe. This plate is set in another plate, and is provided with a rack and pinion. as shown, by which it may be moved longitudinally. The whole is placed on top of the main flue, the partition-wad in which is located between the two openings referred to. A shifting of the pipe and the plate to which it is attached enables the operator to cut off completely the connection between the two adjoining parts of the main flue.