The general arrangement of a blast furnace plant in the Cleveland district is shown in fig. 4. The ore to be treated is brought into the works by the mineral sidings shown, and passes by means of the hoist to the top of the calciners, five of which are shown in the plan. The waggons, when emptied, pass away by means of the drop, while the ore after passing through the calciner is taken to the blast furnaces, three of which are shown in the illustration. In connection with each blast furnace are two hot-blast stoves for heating the air which is supplied by the blast engine situated in the engine-house. The iron produced by the blast furnace is cast in pig beds in front of the furnace, and is carried away on the lines of rails shown, while the slag is disposed of by a machine by which it is granulated, and in this form it is now generally used for ballast or for the production of slag cement.

In this plant the fuel used is coke, but in some cases raw coal is employed, and it is then found advantageous to provide a condensing and washing plant, so as to extract the ammonia and tar from the gases before they are used for firing the boilers. Plants for dealing with part of the gases from coke furnaces are coming into pretty general use, as the gases when collected and cleaned can, without difficulty, be used in gas engines for supplying blast or for many other purposes around the works.

In fig. 5 is given a section of the fairly typical arrangement of a portion of a Southern American blast furnace plant erected about 1890. It will be seen that the furnace is of what is called the cupola type, having comparatively thin walls which are steeply inclined, and that it is provided at the top with a cup and cone charging arrangement so as to allow of the collection of the gases, which are taken to the stores and boilers by means of the wide pipe or downcomer, to the bottom of which a dust catcher is attached. To each furnace three fire-brick stoves with separate chimneys are provided. The blast is conducted from the stoves to the furnace by means of the blast pipe shown, and enters the furnace through twyers placed around the hearth, while water blocks are introduced in the inclined sides or boshes of the furnace in order that the lining may be kept cool and the shape preserved. In this plant the stock-yard and pig-beds are covered, while the waste gases from the furnace are conducted along an underground flue. It will be noted that no calciners are provided in this plant.

The general arrangement of a modern American blast furnace

plant of considerable size will be understood by reference to the plan of the celebrated Edgar Thompson Works, near Pittsburg, Pa., which is given in fig. 6. This plant includes nine blast furnaces, and in addition, two other furnaces have been recently erected on an adjoining piece of land, not included in this plan. The furnaces are known by the letters from A to I, and with the exception of A, which makes spiegel, and consequently has a smaller output, they all produce pig iron of Bessemer quality. The furnaces are arranged in pairs, each pair being provided with separate boilers, while there is a separate blowing engine to each furnace.

As the

FIG. 5.-Section of Blast Furnace, Alabama, U.S.A.

ore used is chiefly obtained from the Lake Superior district, and is rich and free from moisture and carbon dioxide, calciners are not required, but large stock-yards are provided. Suitable hoisting arrangements and railways are arranged for handling the ore, and for dealing with the pig iron and slag produced by the furnaces.

Although it has been possible in this brief survey only to give a very general outline of the sources of supply and properties of iron ores, and of the arrangements of a modern iron works, it is hoped that sufficient has been said to render intelligible the somewhat more detailed description of the process of iron smelting, which will form the chief part of the subject-matter of the second lecture.

LECTURE II.

THE BLAST FURNACE.

MATERIALS EMPLOYED.

REACTIONS OF

THE BLAST FURNACE. CHARGING THE BLAST FURNACE. THE BLAST USED IN THE BLAST FURNACE. TAPPING. PRODUCTS OF THE BLAST FURNACE.

WASTE GASES. CINDER. CAST

IRON. GRADING PIG IRON. CONNECTION BETWEEN GRADING AND CHEMICAL COMPOSITION. DENSITY. UNRELIABILITY OF FRACTURE AS A TEST OF QUALITY.