feet in length, its name conveying an idea of its condition, which is rough and imperfect.

The bloom may be broken down under the hammer, instead of rollers; for this purpose, the shingler works the bloom as long as the heat will permit, when it is re-heated and hammered, until it is reduced to one or more anconies, according to the size of bar which it is intended to make; these are again heated, and reduced to the required size and shape.

PILING. To prepare rough bars for this operation, they are cut, either hot or cold, by means of a strong pair of shears, into such lengths as are best adapted to the size of the finished bar required; the sheared bars are piled, one over the other, to the number of from two to six or more pieces, according to the size required, when the pile is ready for

BALLING. This operation is performed in the balling furnace, which is similar to the puddling furnace, except that its bottom or hearth is made up, from time to time, with sand instead of cast iron; it is used to give a welding heat to the piles, to prepare them for rolling.

FINISHING ROLLS.-The balls are passed successively between rollers of various forms and sizes, according to the shape of the finished bar required.

These bars are straightened on a cast iron bed, with heavy wooden beetles.

PROPERTIES OF IRON.

All iron contains more or less carbon, the hardest containing the least, and the proportion varies from 1 to 2 per cent. It melts at 160° Wedgewood; it expands 1th from 0° to 2120 Fahr., andth part, from 0 to a red heat. Specific gravity 7,788.

To test the Quality of Bar Iron.-The most convenient test is by the fracture; but this is not always sufficient, as the same iron will present different appearances, according to the manner in which it has been forged, and the degree of heat to which it has been subjected. In testing by the fracture, the sample should be 1 inch square, or if flat bar, inch thick; cut a notch on one side with a cold chisel, and bend the bar down over the edge of an anvil, or give it a heavy blow, when laying flat on the ground, with a sledge hammer; if the fracture exhibits long silky fibres, of a leaden-gray color, cohering together, and twisting or pulling apart before breaking, it denotes & tough, soft iron, which is easy to work and hard to break, suitable for sheet iron, wire, &c. ; but it may weld badly. A medium, even grain, mixed with fibres as above, but without bright specks or dark spots, is also a favorable indication. In general, a short, blackish fibre indicates iron badly refined, and mixed with carbon, plumbago, or oxyd; if worked very hot, it may be improved, but there will be a great waste. A very fine, close grain, denotes a hard, steely iron, which is apt to be cold-short, hard to work with the hammer or file A coarse grain, with a brilliant, crystalized fracture, or yellow or

brown spots, denotes a brittle iron, inclined to be cold-short, but working easily when heated, and making a good weld. Numerous cracks on the edges of the bar generally indicate a hot-short iron, which cracks or breaks when punched or worked at a red heat, and will not weld; it is strong when cold, and may be useful in that state; but, if worked, care should be taken not to subject it to strains at a red heat. Blisters, flaws, and cinder holes, are caused by imperfect welding at too low a heat, or by the iron not being properly worked, and do not always indicate an inferior quality. The above-mentioned characters are not often found separate in iron, and its quality must be determined by their combination, and by the predominance of one or the other of them. In general, good iron is readily heated, is soft under the hammer, and throws out but few sparks when taken from the fire.

The best test for iron, is to have a piece forged into the shape in which it is intended to be used. Another test for iron, when cold, is to cut a screw thread on a square bar, aud bend it by striking the end with a hammer; also, by punching or drilling pieces which are to have holes in them; in the case of the square bar, it should be bent in different directions, at sharp angles; and if the bar is heavy, place the end on the corner of the anvil, and strike it with a heavy sledge until the piece is forced off. Examine the welding of pieces which are jumped on, or upset.

To test Iron when hot.-Draw out the iron, bend and twist it; split it, and turn back the two parts, to see if the split extends up; punch a long hole in the direction of the fibre, and another at right angles to it; punch holes of different forms; weld the iron to iron and steel; make chains from small rods; observe if cracks or flaws weld easily; finally, forge some of the most difficult pieces for which the iron is intended.

NOTE ON FORGING.-Good iron is often injured by being unskillfully worked; care should be taken that the iron, while heating, is not exposed to the air, which would assist in forming scales of oxyd on its surface. It is to prevent this, that the workman, from time to time, throws sand or clay on his iron to protect it. When iron is at a white heat, immediate contact with coal tends to carbonize it, and make it steely. Iron heated for any purpose, and especially for welding, should be heated as rapidly as possible, in order to expose it the least possible time to the action of the air and coal; for this purpose, the strongest fuel, with an abundant, steady blast, is necessary. Defects in iron, caused by unskillful working, may be remedied in part: if, for example, iron has been burned, give it a smart heat, protected as much as possible from the air; if the iron has been injured by cold hammering, a moderate annealing heat will restore it; if the iron has become hard and steely, give it one or more smart heats, to extract the carbon.

Iron castings for ordnance from the smelting furnace. differing from each other by cipal divisions are gray and fracture when recent.

CAST IRON.

purposes are made of pig metal obtained There are many varieties of cast iron, almost insensible shades; the two prinwhite, so called from the color of the

Gray Iron is softer and less brittle than white iron; it is in a slight degree malleable and flexible, and is not sonorous; it can be easily drilled and turned in the lathe, and does not resist the file. It has a brilliant fracture, of a gray, or sometimes a bluish-gray color; the color is lighter as the grain becomes closer, and its hardness increases at the same time. A coarse grain, without much luster, indicates a good quality of gray metal; a small, white, shining grain, the contrary. Its mean specific gravity is 7,200.

Gray iron melts at a higher heat than white iron, becomes more fluid, and preserves its fluidity longer; it runs smoothly; the color of the fluid metal is red, and it is deeper in proportion as the heat is lower; it does not stick to the ladle; it fills the molds well, contracts less, and contains fewer cavities than the white iron; the edges of a casting are sharp, and the surface smooth, convex, and covered with carburet of iron. Gray iron is the only kind suitable for making castings which require great strength, such as cannon. Its tenacity is increased by annealing at a red heat; but at a white heat it becomes brittle, and acquires a permanent increase of bulk.

White Iron is very brittle and sonorous; it resists the file and the chisel, and is susceptible of a high polish; the surface of a casting is concave the fracture presents a silvery appearance, generally fine grained and compact, sometimes radiating or lamellar. Its mean specific gravity is 7,500.

When melted, it is white, and throws off a great number of sparks; its qualities are the reverse of those of gray iron; it is therefore unsuitable for ordnance purposes.

Mottled Iron is a mixture of white and gray; it has a spotted appearance; it flows well, and with few sparks; the casting has a plane surface, with edges slightly rounded. It is suitable for making shot and shells.

Besides these general divisions, the manufacturers distinguish more particularly the different varieties of pig metal by numbers, according to their relative hardness.

No. 1 is the softest iron, possessing in the highest degree the qualities described as belonging to gray iron; it has not much strength but on account of its fluidity when melted, and of its mixing advantageously with old or scrap iron, and with the harder kinds of cast iron, it is of great use to the founder, and commands the highest price.

No. 2 is harder, closer grained, and stronger than No. 1; it has a gray color, and considerable luster. It is the kind of iron most suitable in general for making shot and shells.

No. 3 is still harder than No. 2; its color is gray, but inclining to white; it has considerable strength, but it is principally used by the founder for mixing with other kinds of iron.

No. 4 is bright iron.

No. 5, mottled.

No. 6, white, which is unfit for general use by itself.

The qualities of these various kinds of iron seem to depend on the proportion of carbon, and on the state in which it is found in the metal. In the darker kinds of iron, where the proportion is sometimes seven per cent. of carbon, it exists partly in the state of graphite or plumbago, which makes the iron soft. In white iron, the carbon is thoroughly combined with the metal, as in steel.

Cast iron frequently retains a portion of foreign ingredients from the ore, such as earths, or oxyds of other metals, and sometimes sulphur and phosphorus, which are all injurious to its quality. Sulphur hardens the iron, and, unless in a very small proportion, destroys its tenacity.

These foreign substances, and also a portion of the carbon, are separated by melting the iron in contact with air, and soft iron is thus rendered harder and stronger. The effect of remelting varies with the nature of the iron and the kind of ore from which it has been extracted that from the hard ore, such as the magnetic oxyds, undergoes less alteration than that from the hematites; the latter being sometimes changed from No. 1 to white by a single remelting in the air furnace. The kind of iron most suitable for any special purpose, such as the casting of cannon, should be ascertained by trial for that purpose in the furnace in which it is to be used.

All cast iron expands forcibly at the moment of becoming solid, and again contracts in cooling; gray iron, as before remarked, expands more and contracts less than other iron.

The color and texture of cast iron depend greatly on the size of the casting and the rapidity of cooling; a small casting, which cools quickly, is almost always white, and the surface of large castings partakes more of the qualities of white metal than the interior.

STEEL.

Steel is a compound of iron and carbon, in which the proportion of the latter is from five to one per cent., and even less, in some kinds. Steel may be distinguished from iron by its fine grain; its susceptibility of hardening by immersion, when hot, into cold water; and with certainty, by the action of dilute nitric acid, which leaves a black spot on steel, and on iron a spot which is lighter colored in proportion as the iron contains less carbon.

There are many varieties of steel, the principal of which are:

Natural steel, which is obtained by reducing the rich and pure kinds of iron ore with charcoal, and refining the cast iron, so as to deprive it of a sufficient portion of carbon to bring it to a malleable state. It is made principally in Germany, and is used for making files and other tools.

The India steel called Wootz is said to be a natural steel, containing a small portion of other metals.

Blistered Steel, or steel of cementation, is prepared by the direct combination of iron and carbon. For this purpose, the iron in bars is put in layers alternating with powdered charcoal, in a close furnace, and exposed for seven or eight days to a heat of about 700 Wedgewood, and then suffered to cool for as many days more. The bars, on being taken out, are covered with blisters, have acquired a brittle quality, and exhibit in the fracture a uniform crystalline appearance. The degree of carbonization is varied according to the purposes for which the steel is intended, and the best qualities of iron (Russian and Swedish) are used for the finest kinds of steel.

Tilted Steel is made from blistered steel, moderately heated, and subjected to the action of a tilt hammer, by which means its tenacity and density are increased, and it is thus adapted to use.

Shear Steel is made from blistered or natural steel, refined by piling thin bars into faggots, which are brought to a welding heat in a reverberatory furnace, and hammered or rolled again into bars: this operation is repeated several times to produce the finest kinds of shear steel, which are distinguished by the names of half-shear, single-shear, and double-shear, or steel of 1 mark, of 2 marks, of 3 marks, &c., according to the number of times it has been piled.

Cast Steel, is made by breaking blistered steel into small pieces, and melting it in close crucibles, from which it is poured into iron moulds; the ingot is then reduced to a bar by hammering or rolling, as described under the head of malleable iron, these operations being performed with great care. Cast steel is the finest kind of steel, and best adapted for most purposes; it is known by a very fine, even, and close grain, and a silvery homogeneous fracture; it is very brittle, and acquires extreme hardness, but is difficult to weld without the use of a flux. The other kinds of steel have a similar appearance to cast steel, but the grain is coarser and less homogeneous; they are softer and less brittle, and weld more readily. A fibrous or lamellar appearance in the fracture indicates an imperfect steel. A material of great toughness and elasticity, as well as hardness, is made by forging together steel and iron, forming the celebrated damask steel, which is used for sword blades, springs, &c.; the damasked appearance is produced by the action of a diluted acid, which gives a black tint to the steel parts, whilst the iron remains white. Various fancy steels, or alloys of steel with silver, platina, rhodium, aluminium, have been made with a view to imitating the Damascus steel, wootz, &c., and improving the fabrication of some of the finer kinds of surgical and other instruments.

PROPERTIES OF STEEL.

The best steel possesses the following characters: heated to redness, and plunged into cold water, it becomes hard enough to scratch glass, and to resist the best files; the hardness is uniform throughout the piece after being tempered, it is not easily broken; it welds readily; it does not crack or split; it bears a very high heat, and