The workmanship is of a finished and accurate character all rivets completely filling the holes, which are slightly countersunk under the rivet heads, all holes in the plates and flanges being perfectly fair with each other, and no drifting is allowed, in the accepted sense of the term, on any consideration. If any of the holes are not perfectly fair with each other, they are rimered until they become so, care being taken that after rimering, the rivets shall completely fill the holes. All the plates are brought well together before any rivets are put in. Outside edges of holes are slightly countersunk and all burrs removed. The pitch of the rivets and the lap of the plates are shown in the detail drawings, Figs. 1-5, and rivets are countersunk only where mentioned on the drawings, see Fig. 13. The edges of all the plates are planed, turned, or shaped to an angle of one in eight before being put together, so as to leave a full edge for fullering, which is done with a broad-faced fuller actuated by pneumatic pressure, the ordinary caulking tool being dispensed with. It is quite unnecessary to go into the various rules and data used in the workshop by the workman in getting circumferences, etc, as these can readily he turned up in the various hooks published for the boiler-maker.

After the plates are delivered from the mill floor to the boiler yard, having been rolled and sheared in lengths and widths according to the position they will eventually occupy, they are at once taken in hand, and where necessary, the small amount of buckle that may remain in them, is taken out and otherwise straightened.

If a plate is buckled in the middle the edges have to be elongated, and if the edges are buckled the operation is vice versa, a plater placing his flatter where his judgment indicates, and gradually elongating wherever required, which often occupies hours of tedious work. This process is greatly shortened by a multiple roller straightening machine, the lower surfaces on the top set of rolls being arranged to come slightly below the top of the bottom rolls, and the plate is therefore passed through the series in a serpentine manner. By adjusting the top rolls, the plate can he made to come out almost perfectly straight, hut the buckle is not absolutely removed, although the work is done very effectually, especially on « inch and ¬ inch plates, saving many hours of hard labour. No matter how bad the plate was, it requires very little manipulation by the plater after it leaves the machine. It removes the waviness, takes out the lumps and hollows, and appears to concentrate or make the buckle more defined, and this generally towards the end, giving the plater a very good idea where to place his flatter; whereas without the machine, the plater might be hammering for hours, even before he got to the buckle. The machine appears to act more effectually when the buckle is in the middle of the plate, elongating the edges in a greater proportion than it would the middle supposing the edges were buckled.

The barrel may be made telescopic, as shown in the general drawing, and of three plates, or, as in some cases, with only two, each about 5 feet 6 inches long, butting together, covered by and riveted to a weldless ring, the longitudinal scam being welded. The transverse joints are single riveted, Figs. 2-5; longitudinal seams are butt jointed, with inside and outside butt strips, and these break joint on each side of the centre line of the boiler at the top, as shown in Fig. 5. The seam joining the barrel to the firebox casing is zigzag riveted, Figs. 5 and 6. A strengthening ring or plate « inch thick is riveted to the inside of the middle barrel, as per detail drawing Fig. 5, about the dome hole, which hole does not exceed 19 inches by 22 inches. The barrel plate3 are then taken and examined for surface and buckle, and invariably found to be sufficiently straight for machine purposes. The plates are ordered to be sheared with an extra half inch in width and length, in order to get the plate square with the template. A batch of five is then taken and the top one marked for drilling the holes, every hole required being marked and drilled at a radial or specially designed drilling machine.

It is a very convenient practice to drill the first or future template half through with a ¬-inch drill, and then follow on through the batch with the full-size twist drill. If the full-size drill is used first, the point, being so broad and not actually a cutting edge, is very liable to run, and then of course, it has to be drawn with hammer and chisel The first batch having been drilled, the top plate is used for the template of the next four or five sets of five, and the second plate of the first batch reserved for a future template, it being as true as the original. This mode has now been abandoned in favour of a specially designed multiple drilling machine, by which the pitch is secured by a lock upon the side of the machine, and is therefore absolutely correct. This refers to the barrel and outside fire-box shell plates, care being taken when marking out the pitch of the rivets in the transverse joints, to get the plates with increased diameters divided equally into the same number of rivet holes. Where punching is practised in using iron plates, in all eases the plates must be punched from the opposite side, that is, the one from the inside, the other - being lapped by the first - from the outside, otherwise the least diameter would not be brought together, and consequently the rivet would not completely fill the hole. It is also the practice in some large works to punch the holes of a less diameter than required, and after the plates are bent and fitted together, to rimer them out by specially designed machinery. In other works the drilling operation takes place at a specially designed self-acting shell-drilling machine, after the plates have been bent and fitted together, twist drills being used, the machine being capable of drilling both the longitudinal and transverse joints. This machine consists of a table, upon which the shell rests, like a wheel lathe chuck with dogs, which receives a motion upon the same principle as that of the wheel-cutting machine. The drill is attached to a slide capable of vertical movement, which is fixed to an upright having horizontal traverse, this latter movement only taking place as the diameter of the shell increases or decreases, the feed of the drill being accomplished by means of screw and suitable gear. The drills of this machine are generally multiple.

Fig. 6.