The vessels when cut through present a nearly uniform section, and which may be thus explained as regards the cylindrical vessel. If the disk of 9 inches diameter could have its margin folded up without puckering, it would have a rim of 1 1/2 inches high, the upper edge being of twice the primary thickness, as in fig. 271, page 400, but the stretching from the dies, causes the height of the side3 to become 3 inches, and therefore this tapering thickness is gradually drawn out, as in tube drawing, to constitute the increased height.

In proof of the complete efficacy of the mode, it may be stated that vessels may be thus made in sheet-iron (known as charcoal-iron), a material far less tractible than copper and brass. Great difficulty was experienced in carrying out this alternation of the two processes of stamping and burnishing to form when working with iron, owing to the scaling or oxidation of surface which resulted from the annealing, and which roughness tended to prevent the employment of burnishers. This difficulty was, after various trials, obviated by annealing after the method practised in annealing articles made of malleable cast-iron, (see pages 259, 260,) in which case the ductility and tenacity of the sheet-iron are preserved, and that with a surface quite unimpaired by the firing. The patentee prefers for the annealing mixture, one part of pulverised iron-ore, added to eight of coke or lime, and he gives the preference to that iron-ore which has been once used for annealing cast-iron.

So completely successful are the combined processes, that extinguishers have been thus raised from round disks of sheet-iron, and of course without a seam; the method of stamping with dies having the bevilled mouth and shoulder b b, fig. 974, enables Teasels to be raised much higher than by any other method of stamping, even when burnishing to form is not employed in connection with the stamping.

Note AD, page 431. - To follow the first paragraph. {Drawing taper brass tubes for locomotive engines.)

Some of the brass tubes for locomotives, are made cylindrical without and a little taper within, the metal for them is cast hollow, and drawn on a taper triblet through an ordinary plat*. The thick end is placed near the fire-box, that the tube may be the longer in wasting away from the action of the fire, and also that cinders capable of entering its smaller end may readily escape at the larger.

Note AE, page 431. - To follow the second paragraph. (Rand's Patent Collapsible Tubes.)

These thin tubes are closed at the one end by a convex disk with a projecting screw; the screw being perforated for the expulsion of artists' colours or other matters inclosed in the vessels. They were first drawn as tubes, as described in the text, and the ends were east and soldered in; but the entire vessel is now made by means of only two blows, in dies of appropriate kinds.

By one blow of a screw press, a thick circular disk of tin of the external diameter of the intended vessel is punched out, made concave, and perforated with a central hole, somewhat like a washer for machinery.

By a second blow, the blank or button is converted into the finished tube. The bottom tool is a mould with a shallow cylindrical cavity of the same diameter as the button of tin, and terminating in a hollow screw; the upper tool is a cylinder exceeding the length of the tube, and with a small taper spindle of the diameter of the hole. The cylinder is just so much smaller than the mould as to leave an annular space equal to the intended thickness of the tube. The very soft ductile tin, when submitted to great pressure in the contracted space within the mould, follows the laws of liquids, and may be said literally to flow through the annular crevice, and up the cylindrical mandril, as indeed the formation of the tube appears to be instantaneous, and is a beautiful example both of true principle, and accurate workmanship in the means employed.

The tube is released from the mould, first by the ascent of the cylinder, which leaves the tube behind; and the screwed extremity of the mould is then driven up by a ram and lever from below, and the screwed dies being divided on their diameter, instantly fall away from the vessel thus elegantly produced by a mode which was only attained after repeated variations in the process, respectively secured by patents. Small tubes are thus made in screw presses, and large tubes in hydrostatic presses of proportionate strength.

Note AF, page 433. - To follow the third paragraph. {Clay props used by the Asiatics instead of binding wire in soldering.) "The Asiatic goldsmiths seldom use binding wire for light work, they have always beside them a little dish of a tempered mixture of clay and sand or powdered brick, with little portions of which they form connections and supports for the pieces they mean to solder together. Thus if two tubes have to be joined in the form of the letter T, (inverted whilst being soldered,) they first warm the lower piece, and then dab on a little at a time of the mortar, (leaving the joint clean,) until the inclined props of the clay run high enough nearly to touch the upright piece, which being warmed and set in its place, the connection is completed by a further addition of the mortar, which, when heated over charcoal, becomes quits firm and supports the pieces whilst the solder is running, even in works of pretty considerable size." Sir John Robison.

Note AG, page 444. - To precede Section IV. {Pumice-stone used by Dentists instead of Charcoal, as a support in soldering.)

Dentists are much in the habit of using a lump of pumice-stone as the support in soldering the gold work to which artificial teeth are attached. The pumice-stone is usually filed or rubbed to a flat surface, and the work when laid on this incombustible support, and subjected to the action of the blowpipe, receives a more moderate heat than when laid on charcoal; which latter support is less convenient, as it loses its form from burning continually away, and because at the same time, owing to its combustion, it reverberates more heat than is required by the dentists for their particular purpose.