THE following description of lead burning is taken from my " Lectures." 1. " A very valuable method of soldering metallic substances was invented in France, in 1838, by the Count de Richemont. This airo-hydrogen blow-pipe was called by the inventor the ' Chalumeau Aer-hydrique.' The English patent for this invention was taken out in the name of Luke Hebert, in 1838. But Mr. Mallet claims to have used a similar apparatus prior to 1833. The soldering done by this instrument is improperly called autogenous , soldering. As I shall speak simply of lead joinings - though it is used for uniting various metals - I shall speak of it as lead burning, the name by which it is known in the trade.

Fig. 6. - AlRO-HYDROGEN BLOW-PIPE AND APPARATUS.

"An apparatus complete is illustrated in fig. 6, from one of those now in the possession of my firm. It consists of a self-acting and self-regulating gas generator, a b c, for giving a continuous current of hydrogen gas, through the forked-shaped blow-pipe, d, and of a pair of bellows, e, for supplying atmospheric air (through the same blow-pipe) for the combustion of the gases. The organist found to his cost that the organ-blower played an important part in producing his music, and the burner, or solderer, will find, in using this apparatus, that his burning will depend much upon the blower.

"A good steady stream of air is required to be sent through the tubing, x a, for the proper combustion of the gases. Stop-cocks are fixed at s s, in the forked-shape piping, d, to regulate the current of hydrogen from the gas generator, and the stream of air from the bellows. The bent jet-tube can have any sized nozzle, n, screwed to it to suit the work to be done. The india-rubber tubings, a and h, connecting the bellows and hydrogen gas holder with the blow-pipe, can be of any length to suit circumstances. The gas generator is divided into three nearly equal compartments, as shown in the section, a b c. It is about 12 in. by 13 in., and stands just 3 ft. high. The upper and lower reservoirs, A and c, are lined with lead, the lower one, C, being made air-tight. The metals and pipings are united without solder - i.e., by fusion of the metals. A plug is fixed, as shown at b, in the upper reservoir, A, over the communicating-pipe, d, to the lower reservoir, c.

"Diluted sulphuric acid, of the specific gravity 1.16, is put into the upper reservoir, A; and the lower reservoir, c, is filled with zinc clippings through the aperture, e, which is afterwards made air-tight. f is a leaden tube, closed by a cork, and through which the saturated acid is discharged; g is a safety chamber, into which the hydrogen generated in the reservoir, c, is conveyed by means of a tube, m; k is a stop-cock fixed in the tube, m; i is a tube fixed in the safety-chamber, g, with a cork stopper, which acts as a safety-valve to prevent explosion; p is a perforated false bottom, which supports the zinc clippings in the lower reservoir, c; n is the brass jet-tube, screwed to fit the various-sized nozzles through which the gaseous mixture escapes.

"The apparatus, fig. 6, is charged, when in use, by putting 7 lbs. of zinc clippings into the lower reservoir, c, through the aperture, e, 3 quarts of water and 1 1/2 pints of sulphuric acid into the upper reservoir, A. A pint of acid is added about every two hours. The zinc lasts eight or ten days. The saturated acid should be drawn off after each usage.

"Very intense and forcible jets of flame can be obtained by this airo-hydrogen blow-pipe, at any rate sufficient to melt strong platina wire. For neat burning, it is important to have the right flame-jet. When applied to a bit of shaved lead, the heated point becomes immediately as bright as silver. The following test will indicate with certainty if the mixture and the force of the current be duly regulated; e.g., when the hottest and most reductive point of the interior flame is applied to a piece of shaved lead, the heated point becomes immediately as bright as silver, and the flame itself assumes a violet tint, produced by the volatilization of a small portion of the lead. When there is too much or too little air, the heat is not so intense or pointed, and the melting spreads over a larger surface owing to its being heated more slowly.

"Two pieces of lead can be united when they only butt against each other, as shown at f, but it is better in many cases to make one piece lap over the other. The parts to be united should be shaved bright (the width required for the burning), and a narrow strip of thin lead, as shown at t, shaved bright, should be held in the left hand for supplying the lead required for filling up the uneven space of the joining, or for making a raised seam. In lining cisterns and sinks, for burning under this process, the sides and ends should turn on to the bottom a little, say, 1/2 in. to 1 1/2 in., and butt against each other, as shown at g, so as to get a flat surface burning for uniting the bottom with the sides; and the sides of the cistern should be connected with the ends, or the ends with the sides, on the vertical faces, in a diagonal line, for the outer edge of the overlaps of the lower piece to form a base to burn upon."

2. Briggs' patent Solderer, illustrated in fig. 5, is also much used for lead burning. (Chap. IV. Art. 4.)

3. For lining tanks for chemical purposes the plumber should be extremely careful to see that he obtains sheets manufactured from refined pig lead.

4. For a plumber to fully furnish himself with the knowledge essential to the efficient execution of every piece of work that comes within his vocation may well overwhelm the young student plumber with some concern for his competence, both of brains and money, in after life. But lead burning is so useful an art, that in addition to his other accomplishments he should endeavour to add to them the knowledge of uniting pieces of metal with a metal of the same kind.

5. Lead burning is especially adapted for joining the edges of two pieces of lead together where it would be difficult to lap the lead properly to keep out the weather, as in covering cornices, carved wood pinnacles and finials, balustrades, etc. And for lining tanks with lead for chemical works, where it is absolutely essential that no solder be used, it is the only method of joining the several pieces of lead together. Lead pipes for chemical works should also be united by burning them together with lead, and this the skilful lead burner can very well do.

6. Two pieces of lead can easily be burnt together with the aid of a hatchet-shaped copper-bit. To do this, shave the edges to be united, put a piece of brown paper under the joining, and pull a copper-bit - heated nearly red-hot - along the edges, using a narrow strip of thin lead, well shaved, for making good the seam. The tinned edges of the copper-bit should be preserved as much as possible, and they should be brightened up, by pulling the end of a stick of fine solder over them, before commencing the burning.