To give a large number of instructions to a learner before he begins to work involves a waste of time; because he cannot appreciate or understand everything that is told him until he has performed something. If he has tried to make an article and failed, he will probably perceive the cause of failure when pointed out to him. But these causes of failure are very little heeded by some individuals until they have really experienced the things mentioned to them. Hence arises the necessity of giving as many instructions to a learner as he can comprehend or make use of at the moment he receives them, but no more than the proper number, if that number can be ascertained.

When a learner has knocked about a few pieces of iron or steel upon the anvil, possibly made a few articles, and discovers that if he possessed a little more machinery he could make a few more, he is in a condition to attend to a few remarks about his tools. It is scarcely possible for him to begin forging by making his own tools, except to a very limited extent; but, as he progresses, he will become gradually able to make all he requires. At his present stage of progress he should consider his hammer and tongs, to ascertain if his hammer-handle is tightly fixed in the opening, or whether he has knocked out the wedge through striking the anvil too often instead of the work ; also whether the rivets of his tongs are injured or broken by his own ill-treatment of them. He should not attempt any work that requires the sledge-hammer until he is provided with good tongs and rings to hold them tightly together ; these will prevent the sledgehammer driving out the work from the tongs into contact with some person's limbs. There are three kinds of tools that he can now make in a tolerable manner for his own use; these are straight-edges, squares, and callipers. Before commencing to make these necessary articles, he can make his handle tight, if it requires it, by making a wedge with ragged edges, either of ash or iron, remembering that the wedge must be of very gradual taper, as it is termed, signifying that the angle subtended by the two sides of the wedge should be five or six degrees. When the angle of the wedge is too great, there is danger of it soon tumbling out, and the hammer flying off to the injury of life or limb. As he advances in knowledge, he will learn how to make the opening of his hammer, so that the handle shall properly fit, and also how to make the hammer itself; but at present he must be content by making the wedge only. Having made his hammer safe, he can make a rivet for his tongs by fitting a pin to the two holes and allowing sufficient length of iron each side to form the two heads, at which time, while the tongs are apart, he can notice their form, which will probably teach him how to make a new pair. No tongs is required to hold the rivet or pin while he is making it, because he can provide a piece of iron or steel of sufficient length to hold in his hand.

He should now make, firstly, his callipers, two or three pairs; secondly, straight-edges, one or two ; and, thirdly, a square, one or two.

The form of the callipers shown by Fig. 57 is merely of a simple character, easily constructed, and suitable for smiths, because a tolerable approach to precision in measuring is quite sufficient. The more scientifically made and valuable kinds of callipers suitable for fitters and turners, will be mentioned in due order.

The smith can make his callipers in his own ordinary mode of punching small holes. It is proper to punch the two holes for the joint-pin P,previous to filing or otherwise finishing the edges of the callipers. When the holes are punched, he can fix in a pin in a temporary manner, in order to hold them together a short time, while he grinds the edges to any required shape by the grindstone. But by careful shaping upon the beak of the anvil, he can avoid grinding the edges ; and it will be only necessary to grind the ragged portions from the two sides that are to be put together while riveting in the joint-pin.

When the callipers are made, the operator can proceed to the straight-edge. This he can also make without proceeding to the erectory or turnery to borrow a straight-edge by which to make his own ; and he can make an edge .sufficiently near to a straight one, without resorting to two or three others, which is the custom if a near approach to precision is required. The mode, among others, resorted to by the author for producing in a remarkably short time a useful instrument, is thus indicated :-

If the tool required is to be twenty inches in length, procure a strip of thick white paper twenty-two inches by four inches wide, and drive two round pins through the ends of the strip of paper on the wall at about nineteen inches between the two pins, so that the line of distance between the two is nearly vertical; but a little to the left of the lower pin is the proper place of the upper one. Smooth the pins with a piece of emery cloth, and fasten a thread of black silk or black smooth cotton to the lower pin, and place the other portion of the thread over the upper pin, and allow the thread to hang with a weight attached, which will be on the left side of the apparatus, if the pin which is uppermost is to the left of the lower one. It is now necessary to drive into the wall, or board, if such is being used, a third smooth pin ; the place of this pin is about half an inch above the lowest one, and half an inch to the right side of it. If all the pins are tight in the wall and the thread stretched tightly on the right-hand sides of the two upper pins, the affair is fit for use by applying an edge or side of any tool that requires some lumps to be taken off. This simple apparatus is capable of being adapted to straight-edges of any length less than twenty inches by driving in another pin at various distances from the upper pin, being careful to push the thread to the right hand while driving in the pin. By a little more contrivance, the thread could be made to subtend a near approach to an angle of ninety degrees to the plane of the horizon: the longitudinal axis of the thread would then be something like a geometer's idea of a straight-edge.

When the smith has ground or filed one edge of the straight-edge to the thread, he can make the opposite edge parallel by using his callipers.

In order to make a square, it is necessary for the smith to procure a piece of sheet iron, or some kind of flat smooth surface, about twelve or eighteen inches across. Describe a circle whose circumference shall reach nearly to the edges of the plate; and then, without any proper knowledge of how to form or construct a right angle, he can divide the circumference into four by his compasses; he can then mark lines across the middle of the circle to the four points, and the angles thus shown will enable him to adjust his square, which will be much nearer to correctness than his forging will at any time require. Fitters' squares are very different instruments, and require quite different treatment, which will be fully demonstrated at the proper time. Probably, the adjusting of a square is of little importance to the smith who is but a learner, when compared to the forging of a square, which is performed in several ways. The simplest method is that by which he should commence, and consists in welding the ends of two thin bars together, so that the one bar shall be at right angles to the other. The next method consists in cutting a slit into the end of a bar to form the thick part of the square, and then welding a thinner bar into the slit in order to form the blade or thin portion of the square.

The squares for fitters are forged of steel, and the blades are fullered down, processes that are included in the portion of this work concerning tool-making.

After the learner has actually forged a few tools, he is also in a condition to understand some remarks concerning the various qualities of iron; and he will, by experience, be enabled to select the particular kind of iron suitable to his particular piece of work in hand. Probably he will have noticed that some pieces of iron are very tough, and require more cutting than other pieces, in order to divide one piece into two, while cold. If this tough kind of iron is also tough while red hot, it is termed the very best kind of iron that can be produced. This kind is that with which the learner should make his tools that do not require to be made of steel. Another variety of iron will bear much twisting and hammering while hot, but very little while cold without breaking. This sort is not suitable for tools or machinery that require much moving or rough usage; but if, after being forged, such iron is to remain fixed, it is a very hard and durable metal. There is another class of iron which is the most troublesome variety with which the forger has to work. It is rather compact and tenacious while cold, but while hot it will split while being punched ; it will break under the hammer; it will crack while being bent; and it is almost useless for welding. But even this kind of iron is useful in the hands of an experienced man who knows to what purposes it should be applied.

The varieties of iron may be thus noticed in a general manner; but the only true method of ascertaining whether an individual piece of iron is suitable for an individual piece of work is by forging a piece of the iron, and applying it to use. Then it is necessary to remember that the qualities of iron become altered during a course of time; the new or the foreign qualities and properties which the iron thus receives are the results of the agencies which have affected it. These agencies are conveniently termed mechanical, chemical, and improper. The mechanical agencies include a large number, such as those to which all pieces of moving machinery are subjected. The chemical agencies include the action of the atmosphere, water, and heat and cold. The improper agencies include ill-usage, such as hammering by careless workmen, improper hardening, and several others.

The quality of the coal influences the quality of the forging. The learner will be much discouraged by the unclean appearance of his work, and the trouble of welding, if he happens to be working with bad coals. He will be enabled to distinguish good from bad, by the ashes and coke which are found. Good coal produces a large quantity of coke, and but little white ashes. Bad coal produce but little coke or cinders, and a large amount of white ashes, Avhich consist of lime and alumina and a few other earthy matters. Bad coal often contains much sulphur, which makes the iron brittle while hot, and prevents it from welding; and there is always a large quantity of clinkers formed by the fusion of the earthy matters which good coal does not contain. The manufacturer, whether large or small, may thus perceive that bad coal is much dearer than good, although the price is greater of the superior article. The name of the coal proper for forging is Tanfield Moor: this coal is remarkably friable, and may be broken by the hands.

It is also proper for the learner to keep his work well covered while in the fire. The work will thus become heated much sooner than if he allowed the heat to be blown up the chimney by the blast. Iron becomes oxidised by long exposure to the fire and air at the same time; consequently, by covering the work properly, coal, time, and metal will be economised.