The solid drawn seamless tube has entirely dispensed with the old brazed seam for locomotive steam pipes. They range from ¾ inch to 7 inches or 8 inches external diameter, and arc a great advance towards the perfect steam pipe, but, owing to the almost universal interest in the brazed seam, it will not be omitted from this section. The seamless tube must be of uniform circumferential thickness and perfectly round. A piece 30 inches long, annealed, and then filled with resin, must withstand bending until extremities meet without showing defects; but if the sample is not annealed it must sustain a deflection of 3 inches when placed upon supports 20 inches apart and loaded in the centre, without showing local contraction, cracks or other defects. The circumferential strength in tension of a hard drawn seamless tube may be taken at about 30 per cent, above that of a carefully made one with a brazed seam, and, even after annealing, this tenacity is only reduced by about 15 per cent., which is due no doubt to the extra mechanical work imparted to the material by drawing. Boiler tubes successfully withstand an internal pressure of 800 lbs. per square inch, and an external of 250 lbs. per square inch, without leakage, being 1¾ inch external diameter,and having a cross-section of about .52 square inch.

Owing to the fact that copper rapidly loses its tenacity at high temperatures, and that the range between a brazing coppersmiths' worK. 181 heat and that when it becomes red-short, or rotten, is narrow, it follows that the value of a pipe with brazed seam is in ratio to the skill of the workman, and perhaps no operation depends so much upon the operator. If this brittle heat should he produced to only a small amount, then any degree of internal stress would produce cracks of various grades of importance, most likely not sufficiently developed to be detected by the hydraulic test, but which would grow by wear and tear, vibration, repeated expansion and contraction, until finally, if not discovered in time, the pipe would burst. The next matter of importance is the scarfing, the length of which depends upon the size and thickness of the plates. In any case both the edges should be bevelled, which, if of medium length, will always make the best joint, because long bevels have a greater tendency to burn. The machine planed scarf makes the most perfect joint, although the paening hammer is responsible for most jobs. It is important to bring both scarfs together so that no gutter is formed; and also it is imperative to bevel both edges, although many pipes may have been made with the inside edge left square, in which case the tendency is for the sharp square edge to cut into the material overlapping it, and increase the liability to rend. For brazing a good clear fire is required, and if there has been any tinning going on before, the operator is careful to remove all traces of that metal from the fire and its precincts, for should he have the misfortune to get a little scrap of tin on to the joint, it will percolate its way through the copper, or combine with the spelter, burrowing, "rat-like," and spoiling the job.

This can be easily demonstrated by placing a small bead of tin upon a thin copper plate over a fire, when it will rapidly eat its way through - a fact readily explained, and realised after a perusal of Part III. of Section IL, "The Brass Foundry," page 96; and needless to state that in a locomotive shop where the work is well regulated it is a most rare occurence. Clean metallic surfaces are in dispensable, because solder spelter will not adhere to anything dirty or greasy, but with tinned surfaces no particular care is needed, as the solder will adhere readily and quickly. There are many hard solders in use adapted for special jobs, either copper, iron, or steel; that for the latter may, of course, be stronger than for the former, but in any case it should be tough and fusible, a lower melting point than the materials brazed being of a necessity, for then risks of burning the scarfs are reduced to a minimum. Borax is generally the fluxing agent used, then, if all due precautions have been observed, the brazed seam of a copper pipe is as strong as the rest of the material; but the extension measured on given lengths will be, even in the best cases, 50 per cent, less than that upon the rest of the material, excluding the seam. This extension and contraction of area takes place upon each side of the seam, leaving it almost perfectly at its original area, breaking in the best joints parallel to the seam, in a straight line at the junction of the bevel with the original thickness, but in the inferior joints the rend is very jagged, and it is to be generally observed that this jagged rend is due to either hollow places where the solder has not penetrated, or where either dirt or flux. has been entrapped, and therefore for these reasons 15 per cent, should be allowed for reduction of tenacity. This of course, relates to copper, it being needless to take this point into consideration in brazing mild steel sheets, as no pressure is required behind them. If that were necessary, welding would enter into the question.

The internal pipes consist of solid drawn tubes ¾ inch to 2 inches diameter, and of Nos. 10 and 11 I.W.G. for the injector and ejector steam, exhaust and delivery, and the blower or jet pipes. A set is put in the ejector exhaust pipe, to escape the washout cooks oh the side of the fire-box.