Through the centre of the valve-face a hole is bored to receive the cylinder trunnion. This trunnion, Fig. 4, is a steel pin screwed into the valve-face of the cylinder (see Fig. 3, section of cylinder showing valve-face and steam-ways). The outer end is threaded for a nut, D; this has a washer beneath it, and keeps the cylinder close against the standard, with the faces of the valves held together steam-tight, yet so that the cylinder may oscillate freely. A spiral spring beneath the nut is sometimes used, but in good work the adjustment is made with a pair of lock-nuts. The hole through the standard must be perfectly at right angles to the face, and the trunnion in the cylinder must also be perpendicular to the valve-face, or the two faces cannot come together steam-tight.

The stuffing-box, 1, of the piston is made with a gland drawn down on the packing by two screws. This arrangement is shown in section at Fig. 5. The method of fitting the gland, whether by screwing direct into the boss of the cylinder cover, as shown at the right in Fig. 5, or by screws tapped through the flange, as in the left-hand illustration, is quite optional. By referring to Fig. 5, the construction of the two forms of stuffing-boxes will be understood. The gland belonging to each is shown separate immediately above the sections. The same lettering is used in both. A is the cylinder cover, with the projecting boss into which the gland B is fitted. The space for the stuffing or packing is marked C. This is filled with lamp cotton, and when the gland is screwed down the cotton is compressed, so that it makes a steam-tight fitting for the piston-rod to slide in. The hole for the piston-rod is shown through the centres of both sections. As before explained, the gland on the left is secured by two screws shown in the section; it is fitted into a plain cylindrical hole. The other gland is threaded to screw direct into the cylinder cover, which is tapped to receive it. The first method is the one always employed in large engines. The screwed gland has a milled edge, so that it may be turned with the thumb and finger.

The action of the valves in a double-action oscillating cylinder will be best explained by reference to Fig. 3. This shows the face of the standard and the section of the cylinder. There is a flat face to the cylinder, usually circular; this has the two steam-ways a, a, bored in it. These holes meet others, drilled from the ends of the cylinder, parallel with its bore, and conduct the steam to the ends of the cylinder through the passages at b, b. On the face of the standard are two holes a and b drilled from the back, one to receive the steam from the boiler, the other to take the exhaust pipe. These holes are not bored through, but communicate with the circular groove c, d. This groove is stopped at e and f. The cylinder is placed against the standard and held close to it, as shown in Fig. 1, by means of the trunnion illustrated by Fig. 4.

When the cylinder is vertical, as shown in Fig. 2, the port-holes are opposite the solid part of the face e and f. Suppose live steam issues from a and fills c, directly the cylinder is moved on one side and one of the port-holes comes over the groove e, the steam enters the cylinder and, pressing against the piston, compels the crank to revolve. By the same motion the other port is uncovered into d, and the dead steam escapes. When the cylinder again reaches a vertical position the steam-ports are again closed, but the momentum of the fly-wheel carries it over the dead centre, and then the positions of the ports are reversed. The one formerly over the exhaust now opens to the live steam and vice versâ. Thus the steam is admitted alternately at both sides of the piston, and so the engine continues to work.

VI.—Model Boilers and their Construction.

A few words on model boilers and their construction will now be advisable. They have been mentioned several times incidentally in the course of these sections, but, with the exception of the small tin boiler for the oscillating engine first described, particulars of their construction have been omitted. It is not an easy task making a steam boiler, and in most cases it will be found cheapest in the end to purchase ready made.

The materials most generally used are brass and copper; sometimes iron, or what amounts to the same thing, tin-plate, is employed. Brass or copper, from the ease with which they can be manipulated, are the best for a beginner to work on.

Brass can be bought in the form of tube of sufficient size for small models, and strong enough to stand the steam pressure. The edges of the bought tube are brazed together, and thus the joint is made nearly as strong as the other part. The tube is afterwards drawn, and, except from a slight discoloration, the joint is not noticeable.

Brass tube, from two inches to six inches in diameter, cut in lengths suited for boilers, is sold by most of the model engineers. The price of the tube ranges from about 2s. per foot for the small to about 10s. per foot for the large size; the short length necessary for a boiler being charged at about the same proportion. This is merely for the tubular body part of the boiler, and it may be placed vertically or horizontally as required.

The ends or flanges which have to be fitted on are extra pieces. Sometimes a plain disc of metal is fixed by soldering with pewter; but this plan should be strenuously avoided. The ends should at least be brazed on. It is best also to use discs with a rim round them to fit over the boiler tube. This gives a much stronger hold than is possible with a plain disc of sheet metal.

Castings used for the boiler ends must be quite free from any flaws, or the weak part will be apt to give way under the steam pressure. It is often advisable to use castings, which may be made of a shape exactly suited to certain requirements. An inverted cup-shaped casting for the lower end of a vertical boiler gives a good heating surface. A flue for the chimney must be put in it, and this goes up to the top end of the boiler, which may appropriately be dome-shaped.

The flue and both ends of the boiler should be brazed in their places, not soft-soldered. Some prefer to use silver solder for such purposes, and this is an excellent material. When the joints are made to fit properly, as they should do before soldering, only very little solder is required to unite the parts. Borax is used as the flux, both for the alloy employed in brazing and for silver solder. The heat required to flow these properly may be got from an ordinary gas jet, with the burner or nipple removed, using a common blow-pipe to urge the flame.

A horizontal boiler is frequently only a plain tube, with the ends soldered in, and supported on legs to raise it sufficiently to allow a lamp to be put underneath. The heat applied in this manner does not take effect as it should. The flame is deflected from the surface of the boiler, and, moreover, any breath of wind stirring will blow the flame aside. A plain saddle-shaped boiler is much better; in this form the heating surface is large, and the heat from the furnace is applied to it direct, and cannot well be deflected.

Flues or tubes are very desirable in any form of boiler, and one or the other should be used. The plain straight chimney put through the boiler is the most simple form of flue. If this is of spiral form, like a corkscrew, the effect is infinitely increased, because the heat, instead of ascending straight up through the vertical tube, is met at every turn with a fresh surface of metal. In winding its way through a spiral tube, the heat is absorbed in a way quite unattainable when a straight tube is used. Several small tubes are of course better than one large one of the same area. By increasing the number of flues the cost of making a boiler is also increased, and it is to save expense that large flues are used.

Boilers for locomotives, which are required to make steam very fast, have an immense number of tubes running through them. The space between the tubes, which is occupied by the water, is often very small, and in fact the tubes are put as closely together as possible. As the heat rushes through them it is absorbed by the water in contact with the tube, and turns it into steam. The greater the heating surface the more readily is the steam generated.

Tubes are often put across the fire-grate; they are then called cross-tubes. Two, placed one above the other and crossing each other, will give a large amount of heating surface. By adding this simple contrivance to a vertical boiler with a straight flue it may be made to give off much more steam. One or two cross-tubes generally suffice to convert a useless boiler, that is, one that will not generate enough steam, into an effective one.

The fuel used to heat small boilers is generally spirits of wine. This is put in a suitable receptacle and burnt through a cotton wick. Several wicks are used in large boilers, and they are placed to heat the largest surface available. Spirit lamps are a source of danger if proper precautions are not taken. Unless there is a free outlet for the air within the lamp, it will be expanded by the heat and cause the spirit to rise too quickly in the wick. Sometimes it will overflow, and then it burns wherever it may be. Care must therefore be exercised in using spirit fuel. In model boats it occasionally happens that the spirit overflows, and the boat is all ablaze. An iron tea-tray, or some such utensil, should be used to stand the boiler on when the furnace is to be lighted.

Charcoal is a better fuel, when there is sufficient space in the fire-box to contain a supply. The waste steam from the cylinder must always be conveyed to the chimney and escape up it to make a draft through the fire. Without this it cannot be made to burn sufficiently fierce for the purpose. A charcoal fire will act very well, with a little attention, and except for the smallest engines it is always preferable to methylated spirit.

As it is not possible to give any adequate instructions on boiler-making in the limited space at my disposal, the above hints are chiefly intended for the guidance of purchasers.

A safety valve should always be fitted to a steam boiler. One of the spring valves has been illustrated in the chapter treating of the small oscillating engine. The lever safety valve is more certain in its action, especially in model work, and is better adapted for stationary purposes. A weighted lever is of no use to a locomotive or marine boiler, as the motion of travelling would disarrange the gear. The safety valve of every engine should be tested frequently, to make sure that it does not stick in its place and that all works perfectly free.

A glass gauge, by which the height of water may be seen at a glance, is frequently attached to boilers having any pretension to high-class workmanship. There is a good deal of work in a properly made gauge, and the cost is correspondingly high. Two or three stop-cocks are required in a gauge, and these involve good workmanship, or they will not stand the pressure. Leaky taps are a sign of inferior work.

Gauge cocks are sometimes used instead of the water gauge just mentioned. These are plain taps with straight noses. Two are wanted on a boiler; they are screwed in, one at high-water and the other at low-water level. By turning on these taps it is easy to see whether the water is within these limits; but the precise height cannot be ascertained. The gauge-glass is therefore much preferable.

Whistles are fitted to boilers only as ornaments. They are quite useless as signals, except such as can be given by word of mouth, are not required in working model engines. These attachments are made to sound by allowing the steam to act as the breath does in common whistles.

Force-pumps are used to force water into the boiler to make up for that converted into steam, and conveyed through the cylinder. These pumps are actuated by an eccentric on the crank-shaft, and, at every revolution of the crank, throw a small quantity of water into the boiler. When we consider how much water is evaporated to make the quantity of steam used for each revolution of the cylinder, we may arrive at an idea of the work required of a force pump. Practically the water to be injected at each stroke is too small to be dealt with, unless a large cylinder has to be supplied. The only way to work a force pump for a model satisfactorily is by gearing, so that a stroke of the plunger is performed about once to each hundred revolutions of the crank.

A better plan for feeding small boilers is by hand. The force pump is attached to the boiler in the usual way, but not connected to the engine. The plunger is worked by a hand lever, and when it is seen that water is wanted in the boiler, a few strokes of the lever will suffice.

Governors are used to control the speed of the engine. Without any such contrivance the engine runs at a speed corresponding to the work it has to do. The heavier the load the slower the speed, and immediately that the load is decreased the speed increases. A governor consists of a pair of balls, which are attached to arms pivoted to an axis revolved by the engine. The faster the speed the greater is the centrifugal force of the balls, and by connecting these with a valve, called a throttle valve, in the steam pipe, the supply of steam is reduced as the speed increases. By this means a uniform rate of speed is attained, irrespective of the steam pressure or the duty demanded of the engine.

CHAPTER X.—THE ‘BOY’S OWN’ MODEL LAUNCH ENGINE.
By H. F. Hobden.

I propose in this chapter to give a few practical hints showing how to build a perfect model of an inverted-cylinder direct-action engine with link-motion reversing gear, like the sketch below, which represents a type in daily use on the river and sea. Such a model, having a fixed cylinder, has not the friction of other types, and therefore it gives more power, size for size, than an oscillating engine, and does not get so easily out of order.

You must of course have a lathe, which I will therefore suppose you to possess; but should there not be a slide-rest to it, you must get the cylinder bored by a professional turner, for which he will charge about two shillings, according to the size of your castings.

Let me first briefly explain the action of the steam in the engine by a diagram (Fig. 1, p. 139). The cylinder A is bolted into the standard, B; the ports or steam-passages are shown at C; and the slide-valve that allows the steam to pass alternately to each side of the piston is marked D, in its case F. G G are the stuffing-boxes, which have to be packed with lamp-cotton greased to make them steam-tight, H is the piston, with its rod finishing in a cross-head J, which is cut with a groove to slide up and down the standards to guide it and prevent the piston-rod being bent out of shape. K shows the connecting-rod, attached at its lower end to the crank L. M is one of the eccentrics working the slide-valve. N is the main shaft, resting on the plummer blocks O O, having a heavy fly-wheel at P and the coupler at Q. R is the top cylinder plate, drilled to screw in the grease-cock, of which I will presently give a drawing on an enlarged scale, S is the bed-plate, T the steam supply, and X the exhaust.

You will observe that the steam is coming in at the top of the cylinder, through the top port, as shown by the arrow, pressing the piston down and allowing the waste steam that has already raised the piston to escape through the lower port, and so into the exhaust. By that time the slide-valve is raised (by the eccentric) sufficiently to cut the steam off from the top port, which by that means is in its turn put in communication with the exhaust, and allows the steam to pass out of the top part of the cylinder, whilst it admits it to the lower portion, and so on alternately.

And now to the practical work. After having the cylinder bored, as already mentioned, get a piece of oak or other hard wood 1¹⁄₂ inch square and about 6 inches long. Turn one end of it in the lathe, so that it fits the inside of cylinder, and drive it on. Then put it in the lathe again, and turn the flanges A (Fig. 2) down, and be very careful that they are quite true and square.

The top and bottom cylinder-covers, with the stuffing-box, come next. Screw a piece of hard wood on the end of your lathe mandrel, turn it down to about a quarter of an inch less in diameter than the flanges of your cylinder, make a small hole for the stuffing-box to be driven in, as in Fig. 3. You can now turn the edge and side—that next the cylinder. The projecting part A is to be the exact size of the diameter of cylinder. When this is done, take it out and place it in another chuck, and drill and turn the stuffing-box out, and screw it to receive the gland (Fig. 4).

Now chuck the top cover and turn it down to size. The piston is a casting, and has to be turned in the lathe to fit the cylinder, and a groove run round it to hold the greased cotton to make it steam-tight. Whilst in the lathe drill a hole in the centre, and tap it to receive the piston-rod, which you can make out of steel wire. Then pass one end through the stuffing-box on cylinder-cover and screw it on the cross-head J (Fig. 1), having first filed it up quite square and true and finished it off with emery. Now take the standards B (Fig. 1), and finish them up with a file in the same way, and be careful that the insides forming the guides for cross-heads are quite true. We can now make the lagging for cylinder. Get a piece of mahogany the length of the outside circumference of cylinder and the width of the distance between flanges of same. Then plane it down to about an eighth of an inch and score it with a penknife every eighth of an inch down its width; it will then bend round the cylinder, and you can fasten it on by a couple of brass bands, screwing the ends down near the slide-valve case.

We will next tackle the steam-ports in the cylinder B (Fig. 2). They are simply two holes drilled side by side until they reach the openings C C (Fig. 2) in the casting; they must not be drilled any farther.

Now place the ends on cylinder and drill through them so as to screw them on to the flanges. The slide-valve case is a casting with separate lid (Fig. 5), and has to be faced up with a file, and four holes drilled through the lid and corners to screw on to the cylinder face. The boss on lid must now be drilled and tapped for steam-pipe to be screwed in.

The slide-valve itself is like Fig. 6, has a hollow cast in its face, and a small projection on the back (B), which you must make a narrow groove in with a saw, and file the end of the valve-rod down to fit it, as shown at C, Fig. 6.

The face of the cylinder and also of the slide-valve must now be made to work steam-tight by rubbing on a perfectly flat stone until true, and then putting some emery and oil on a board and working them up until they are quite true.

The eccentrics may now receive attention. They will require to be chucked twice, and the true centre marked. Do not drill it out yet, as the hole for the crank-shaft must not be in the centre, but half the travel of the slide valve from the centre. For instance, if the valve travelled one inch you would have to drill hole for shaft half an inch out of true centre of eccentric.

The straps (Fig. 7) have to be turned quite true to the size of the groove on eccentrics, then taken out of lathe and cut through line A B with a fine saw, and screwed together at C C. A hole has now to be drilled at D and tapped for the eccentric rods to be screwed into, one of which will have to be bent like Fig. 8, so as to allow it to work on to the quadrant. It is the neatest way to key the eccentrics on to the shaft with a small steel wedge.

The quadrant (Fig. 9) is of brass, and will have to be finished up with a file and emery, and the holes A B B drilled through. The shaft ought to be turned up in the lathe as well as the fly-wheel and coupler, with a slight groove sunk in where the plummer blocks support it, so as to take the thrust.

The reversing quadrant with the lever attached I have shown at Fig. 10. It is best cut out of brass. The notches are cut with a small file after the two pieces have been brazed together with a small piece an eighth of an inch thick between either end. It is then screwed on to the slide-valve case.

The lever is drilled at A, B, and C with small holes, and can be made of flat steel wire; A is for a pin to work into a joint or hinge on bed-plate. B is attached to the hole A (Fig. 9) by a small length of brass rod, so as to work easily. Cut with a slot at each end and then drill like Fig. 11.

The small spring D (Fig. 10) is to keep the ratchet down in place, and is best made from a watch-spring, and the handle F is turned out of some brass wire.

The different-size drills you will require can be easily made from various steel knitting-needles warmed, filed up to shape, and then tempered to a light-straw colour.

We now come to the grease or oil cocks, which I have mentioned before. They can be bought ready finished at most model shops, but for those who like to make everything for themselves, this is the way to proceed. Fig. 12 is a section showing interior oil chamber that allows the cylinder to be oiled without stopping the engine by turning off cock A and opening cock B, then filling with oil; then shutting B and opening A allows the oil to descend into the cylinder and lubricate the surface.

Now for the method. Chuck a piece of brass wire about a quarter of an inch in diameter in the lathe, and turn up to external shape; then turn out cup C and drill through from end to end with fine drill; then enlarge chamber D with small bent graver, and take out of lathe and drill through at right angles to previous hole at A and B with larger drill; then put plugs of brass wire in and fit them with emery and oil; rivet over one end, and the other turn up into a handle. Then turn them in straight line with the oil-cup, and drill through with the small drill again. Tap the end E, and screw into cylinder cover, when it is finished.

To keep the boiler full of water as the fire empties it by driving it off in steam, the usual thing is to use a force-pump worked by an eccentric on shaft; but, as the friction is excessive, it takes a great deal of power away from a model. It is best, therefore, to work it by a hand lever, and the pump may be screwed on to the side of boat, the suction A (Fig. 13) being led through the boat’s side and riveted over, and the supply B brazed into lower part of boiler. C is the lever, and D the plunger, which must be quite true, and turned up in the lathe; likewise the valves E and F and the stuffing-box tapped and drilled. It is best to work it up from a casting, and the outside smooth down with an old file. The projection G will then have to be drilled and the lever pivoted through, having first cut a slot at H to allow the lever to rise and fall.

I will now describe a method of making an injector, or machine for filling the boiler with water by the power of the steam alone, and not in connection with the engine.

The injector was an accidental discovery by a Mr. Gifford, and has now become a universal favourite on board both large and small craft, as it works splendidly without affecting the engine. So you can run the boiler up with water whilst the engine is at rest in harbour or otherwise. And another great advantage over pumps is that the steam, being mixed with the water, raises it in temperature to nearly boiling-point, and so is a great saving in fuel.

Fig. 14 is a section of the instrument as fit for model work, and if you will follow these instructions carefully it will act well.

It consists of three parts—the cone A, the cone B, and the casing C. The steam is admitted at D, and the water at E, the waste water overflows at F, and the hot steam and water is projected with great force into the boiler through the pipe H, which should be led to the bottom of boiler well below low-water mark, and it is quite imperative that the steam-pipe should come from top of boiler as so to get plenty of dry steam, and must not be tapped on to any other pipe.

The injector can be fastened to side of boat by brass band and screws, and the water-supply pipe brought through the side and riveted, as in the case with the pump. The injector will lift water several inches, but it always works better if the water can flow into it freely.

Now we will set to work at it. Take a piece of brass rod and chuck it in the lathe and turn two cones the shape of A and B (Fig. 15). Take them off the lathe and drill A through as far as practicable, and finish with a small rhymer, having first made a small hole right through not larger than a knitting-needle; then tap the port C with an internal screw to take the steam-pipe, and turn a screw on the outside at D.

Now, with the rhymer bore out the conical hollow at E in B, and tap it outside at F and inside at G, in the same manner as the former cone; then drill a small hole right through from end to end, and a smaller one at right angles to the other right through at H. This communicates with the overflow, and takes off the water not carried into the boiler.

Next take a piece of brass tubing five-eighths of an inch in diameter, and turn a screw at each end inside (Fig. 16). The screws turned on the outside of the cones must be the correct size to fit these; then drill a hole at A, and screw in a small tube for water-supply with tap; then drill another at B for the waste water to escape by. Finally, screw in the cone A (Fig. 15) and attach it to the boiler by a pipe, and the nearer the boiler the better, as if the steam condenses before reaching the injector it will stop working. The steam-pipe must of course have a tap to cut off steam when not required.

We must now screw in the lower cone B (Fig. 15) until there is an annular space between the two cones not exceeding a sixteenth of an inch. Then screw in the small pipe at C (Fig. 15), and attach the other end into the boiler below the water-line, where it must have a stop-valve to prevent the water returning.

To start the injector, turn on the water-tap until it runs out of the overflow freely. Then turn on the steam full power, and the overflow will cease, or nearly so. Should it still drip at the overflow, reduce the water supply by the tap accordingly.

It requires carefulness and patience to make an injector, but when done, and working properly, there are few boys with a mechanical turn of mind who would not think themselves well repaid in watching and controlling its mimic action. They would then have an engine fit to show to their most critical friends, and one they might well be proud of; and I shall be content if I have helped in any way to contribute to their happiness.

CHAPTER XI.—THE BOY’S OWN MODEL LOCOMOTIVE, AND HOW TO BUILD IT.
By H. F. Hobden.

Those who class model engines as mere toys, and fit only to amuse the very youngest members of the human family, entirely forget the important place they hold in the estimation of inventors and those interested in mechanism as a means by which they can practically carry out their ideas, because models not only have the advantage of cheapness in construction as compared with the full-sized machine, but also the still greater advantage of being, from the small size and light weights of their parts, capable of construction by the inventor himself without having to employ strangers.

I suppose there is no taste more universal amongst boys, old as well as young, than that for mechanism and engineering. What boy does not feel interested in the models displayed in the various shop windows in our large towns, and what lad with any mechanical bent but has a longing to make one for himself and feels an intense pleasure in being able to do so? And it is with the intention of helping those who would like to build one, but have not the necessary knowledge, that I purpose to explain, as simply as possible, the best method of building model locomotives.

In previous pages of this volume, practical instructions by skilled writers have been given on model stationary engines of a simple make, and also on engines for steamboats, but of all models the locomotive has the greatest charm for most boys, and not unjustly so, as when well finished and carefully painted it has a very handsome appearance, and moreover has the additional charm of its locomotive power.

Those of my readers who have practically carried out the instructions in the previous chapters just referred to, have become, I have no doubt, by this time quite au fait in handling their tools and feel at home in their workshop; but for the benefit of those boys who have had no practical experience, let me give a word or two of advice before we begin our locomotive.

First then, with all engineering work, either large or small, great care must be taken to get the measurements perfectly correct in spacing out the various parts to be joined together, and do not think, because it is only a model you are making, that any off-hand way will do, because you will find before the engine is half finished that great accuracy is necessary if you wish your model to be a working one.

A slight mistake in the measurements of a large engine will cause so much friction as to take half its power to overcome, and the same thing occurring in a model would stop it entirely.

Then with respect to any part you may require to solder, be careful always to make the brass or other metal you wish to unite quite hot. You will then get a good firm joint.

Do not just touch the metal with the soldering iron and then take it away. You might certainly stick the parts together slightly in that way, but they would be sure to come apart the first time they received a blow or any pressure was put on them.

Soldering on the best work should be used very seldom, and all the fastenings should be either done by riveting, screwing, or brazing; and I need hardly remark that no part of a boiler should be soldered which comes in direct contact with the flame of the lamp or furnace.

Brazing, with the exception of very small articles, is beyond the ordinary powers of an amateur.

Even to braze the seams of a model boiler requires a forge fire or very powerful gas-blast, which is too expensive for most boys to get; but small things, such as a broken slide, valve rod, etc., can be easily brazed by using a gas blow-pipe, and as it will cost you very little to make and will prove a useful tool for sweating in solder as well as brazing, I will briefly explain.

Fig. 1 is a section of the blow-pipe complete.

To make it, first get a small piece of brass tube (A) of about half an inch diameter and five inches long; drill a hole at two inches from one end, and insert a piece of gas tube (B) and solder it in place.

Next take a piece of glass tubing a quarter of an inch diameter and about seven inches long, hold one end in a gas flame, and when red-hot draw it out to a fine point, then file round and break off the tip, leaving a small hole.

Next squeeze a sound cork into the tube A as at C, and drill a quarter of an inch hole through its centre and insert the glass tube D, and the blow-pipe is finished. To use it you connect the pipe B with a gas bracket by a rubber tube, and the glass tube D must be fastened to a pair of bellows by means of another piece of rubber tubing; the bellows should have an air-bag attached, to enable you to keep a constant pressure up and prevent having a jerky flame.

When requiring to braze any article, bind the parts together with some very fine brass wire and cover it up with a little powdered borax and water, then lay the article on a piece of charcoal, and if it is necessary to preserve the temper of the steel you are about brazing, cut a potato in half and push each end of the steel rod into the halves, which will prevent the temperature of the rod getting too high.

When you have it all nicely fixed, turn on the gas and light your blow-pipe, immediately work the bellows with your foot, and by either pushing in the glass tube D, or drawing it slightly out, you can regulate the shape of the flame as required.

Then bring the flame to bear on the joint, well supplied with the borax, and soon you will find the brass wire melt and run into the joint like water. It must then be neatly filed up, and the join will be scarcely visible.

Having made this useful tool, I will mention a few others you should get before commencing work; they will not cost much.

A centre punch or pointed steel spike for marking metal for drilling, etc., and a small riveting hammer, three or four files of different degrees of fineness, a screw plate and taps, and also a small hand-drill with a set of drills to fit, will be most useful; and of course very little can be done without a good firm vice.

If you have a lathe, so much the better; it will enable you to save lots of odd coppers for turning various parts. Curves for bending metal on you can easily make from pieces of bar iron, holding them in the vice when working on them.

When you have your tools ready, the materials are required you intend working on, which will consist of several sheets of brass and copper, the castings and various-sized screws and bolts; and having got these all together, we can set to work on our locomotive.

I think it would be better to first give you directions for making a simple one of about fifteen inches, and then to proceed to a more perfect model after.

In a previous article you will find a description of the action of the steam in the cylinder, and although that is in a marine engine, the action is precisely the same in the cylinders of a locomotive, and you should therefore read the description carefully and thoroughly understand it; there is also given a method of turning the cylinders, and hence I shall not describe the process again, but consider that you already know sufficient about it, should you wish to make your cylinders in preference to buying them ready finished.