on a bench with loose bricks, or it may be constructed in a more permanent manner, using an iron shell with fire brick lining instead of loose bricks.

For bench use, there is an insulating layer of bricks laid upon the wood, then an iron plate and then the brick walls of the furnace are laid up. It is only necessary that the bricks are sufficient to hold the flame around the work to be brazed. There is a radiation or reflection of heat from a hot incandescent surface of brick or other material, like charcoal or carbon, which greatly aids in heating the object to be brazed. In fact, it is often impossible to braze certain work with the furnace at hand, until something has been placed around the work to keep the heat where it is needed-hence the use of the confined space in a brazing furnace, instead of letting the flame play directly against the work, in the open.

In Fig. 1, the arrangement of the gas and air pipes is shown. It is necessary that the air should be delivered inside of the jet of gas, as the air thus supplied inside the gas, together with the supply of air outside the jet, enables a much better and hotter flame to be maintained than when the air is delivered wholly around the gas instead of inside it. In the sketch, the two jets are shown controlled by a single valve, each for the air and the gas. Should there be trouble in obtaining the best results with either burner, it can be cured by putting a valve in each of the four pipes leading to the burners. Then it will be possible to adjust separately, the gas and air supply to each burner.

The entire piping may be made up of standard fittings, as shown by Fig. 1, or special castings and forgings. may be provided, as desired. The size of the furnace may be made sufficient to take in the usual work to be brazed,

veloped in the gasoline flame to make a considerable braze. All that is necessary, is to put the heat just where it is needed, and to hold it there. This is best done by building around the work with charcoal which becomes incandescent from the heat of the gasoline flame, and also sets up a heating scheme from its own combustion.

If the article to be brazed, be a very small one, it can be placed bodily in a hole scooped in a bit of charcoal, as

shown by Fig. 3. Here is shown the brazing of a link in a small chain. The broken link is carefully wedged into the hole in the charcoal, and bits of coal may be packed around the link if the latter be comparatively large. The place where the link is to be brazed, is indicated at a, and the heat is applied from the torch b, which, of course, is applied at the most convenient angle.

Another very convenient method of applying charcoal in the brazing operation, is shown by Fig. 4. Here, the work is held between two pieces of hard charcoal

ing the operation. Thus: Free acid causes the joint to "rust out"-something which is fatal to good or lasting work.

The apparatus described above is applicable for braz

The Derry. Collard Co. NY.

Fig. 2. Gasoline torch.

ing heavy work. For light brazing, a simple gasoline torch may be used, as shown by Fig. 2. This appliance gives a very strong flame, but if it be directed upon a piece of iron for an entire day, there would not be sufficient heat to make much of a piece of iron red-hot, to say nothing of melting the spelter. However, there is heat enough de

bearing in mind that the smaller the furnace, the less gas will be required, and the more limited the work that can be done. On the other hand, while the large furnace costs more than the small one, and more piping and more gas is required to properly heat the apparatus, there is always the possibility of filling the large furnace with bricks to fit it to small work and the gas can always be cut down to fit the furnace by means of the valves provided for that purpose. It is in order, then, to provide as large a furnace as there is likelihood of there being work for, then fill up the fire-pot with fire bricks until economy of gas is secured for the particular work to be done. Then, when a large piece of work comes along, take out the bricks, and a large furnace is at hand. The above remarks, of course, apply to job and repair work. For special manufacturing where the same work is to be done day after day, there will, of course, be provided special brazing furnaces, fitted for the particular work in hand. Cleaning work which is to be brazed, is a most important part of the operation. Usually, filing, scraping or grinding must be resorted to. Cleaning by means of acid is sometimes attempted, but this method sometimes proves very far from being satisfactory. If the surfaces are not thoroughly cleaned of grease by the use of strong alkali, the acid will fail to make the entire surface bright, and a poor braze will be the result. Again, if the acid be not entirely removed at the time of cleaning the surfaces, then there will be more trouble, for the acid remaining on the metal will proceed to unite with it into a film of oxide which will not only prevent a perfect braze, but which will probably cause an apparently perfect union to fall apart as the acid left in the metal gets in its work of undermining the layer of brass which has been put upon the work dur

which are clamped firmly upon the work. If the coal is in the way at first, the flame from the torch will quickly burn away the interfering parts. Two or more pieces of metal can be held firmly for brazing by this method, and the charcoal is also brought very close to the point of heating.

A very excellent device for brazing in a shop where there is considerable work, but no gas to do it with, consists of a pair of torch burners attached to a compressed air reservoir of considerable size, as indicated by Fig. 5. The action of this tool is the same as for the torch; it is pumped up after some gasoline has been put into the airtank, then the burners are heated and ignited in the usual way, the necessary air pressure being pumped up in the tank by means of an ordinary bicycle pump-if no better way be rigged in the shop.

Pieces of fire brick, laid on either side of the path of