When you desire to bend the extremity of a tube into a ring you must employ a metallic rod, with which, by pressing on the tube, you separate with a curve, C, (see pl. 1, fig. 14) all the portion A C which is necessary to produce the desired curl. You then successively soften all parts of this curve, and gradually twist it in the direction indicated by the arrow, pressing the iron rod constantly upon the extremity of the curve. When the end A comes into contact with bend C you solder them together at this point, and thus complete the ring. Pl. 2, fig. 27, and pl. 3, fig. 27, exhibit examples of rings formed by this process.
If the tubes which you propose to solder are of a small diameter, pretty equal in size, and have thick sides, it is sufficient, before joining them together, to widen them equally at their extremities, by agitating a metallic rod within them. (Pl. 1, fig. 17.)
But if they have thin sides, or are of a large diameter, the bringing of their sides into juxta-position is very difficult, and the method of soldering just indicated becomes insufficient. In this case you are obliged to seal, and subsequently to pierce, the two ends which you desire to join. The disposition which this operation gives to their sides very much facilitates the soldering.
Finally, when the tubes are of a very different diameter, you must draw out the extremity of the larger and cut it where the part drawn out corresponds in diameter to the tube which it is to be joined to. Pl. 1, fig. 9 and 15, exhibit examples of this mode of adapting tubes to one another.
For lateral solderings you must dispose the tubes in such a manner that the sides of the orifices which you desire to join together coincide with each other completely. See pl. 1, fig. 7.
When the holes are well prepared, you heat at the same time the two parts that are to be soldered together, and join them at the moment when they enter into fusion. You must push them slightly together, and continue to heat successively all their points of contact; whereupon the two tubes soon unite perfectly. As it is almost always necessary, when you desire the soldering to be neatly done, or the joint to be imperceptible, to terminate the operation by blowing, it is proper to prepare the extreme ends of the tubes before-hand. That end of the tube by which you intend to blow should be carefully drawn out, provided it be so large as to render drawing out necessary; and the other end of the tube, if large, should be closed with wax, as in pl. 1, fig. 9, or if small, should be sealed at the lamp (pl. 1, fig. 15). When the points of junction are perfectly softened, and completely incorporated with each other, you introduce a little air into the tube, which produces a swelling at the joint. As soon as this has taken place, you must gently pull the two ends of the joined tube in different directions, by which means the swelled portion at the joint is brought down to the size of the other parts of the tube, so that the whole surface becomes continuous. The soldering is then finished.