by G with the tuyere-holes shown at E in fig. 4, H is the fire-brick lining to the furnace, and I the tapping-hole through which the fluid iron is discharged. In fig. 3, I is the tapping-hole, K the main air-tube leading from the blast-engine, L L perpendicular tubes (marked G in figs. 1 and 2) leading from circular air-passage to tuyere-holes, M is an opening for the insertion of iron into the upper chamber, opposite to opening D in fig. 2, and N the tap for regulating the blast; O indicates the outer casing of wrought iron. When the process is carried only to a certain point, the result is a sort of semi-steel, which the inventor of the process expects will be a very useful article of commerce. Illustration: FIG. 4. HORIZONTAL SECTION OR PLAN OF CONVERTING VESSEL. During the bubbling up of the whole mass of iron and the extreme elevation of temperature caused by the union of the carbon of the impure iron with the oxygen of the air, the oxide of iron as fast as it forms fuses into a sort of glass, and this unites with the earthy matters of the impure iron and floats on the upper part as a flux, thus ridding the cast-iron of all its impurities, with no other fuel than that contained in the iron itself and the air. The accompanying illustration represents a horizontal section or plan of the converting vessel; A the central chamber, B a lining of fire-bricks, C the main air-tube, D the tapping-hole, E the tuyere-holes through which the air is forced into the melted iron to be purified, F is the outside casing of wrought-iron. TIN-PLATE, AND GALVANISED IRON. What is usually called tin is, in fact, sheet-iron coated with tin, and of this tin-plate, kettles, saucepans, &c., are made. The art of coating iron plates with tin has been practised in England hardly more than one hundred years. The very best soft iron is used for the purpose of being tinned. It is rolled out into thin plates, which are cut by shears into squares of usually thirteen inches long and ten broad, these plates are dipped into weak acid to clean their surfaces, then rubbed with sand, and finally washed; they are next dipped into melted tallow, which preserves their surfaces bright till they can be used. They are then immersed in melted tin, which has its surface covered with melted tallow, to keep it from being converted into oxide. When the plates have remained for a short time in the tin, they are removed, and the superfluous tin is wiped from the lower edge with a brush made of hemp, and then cleaned from the grease with dry bran. The objects gained by coating iron with tin are, increased beauty of appearance (for when tinned ware is kept bright, it has almost the color of silver), and a protection to keep the surface from rusting, and consequently being corroded into holes.