To make a hole of any size in a tube, or piercing it, as it is called, you ought to have a sharp pointed flame and a. blow-pipe, which is described farther on.

Cork up one end of the tube, heat the point, see A in Fig. 90, where you want the hole and then stick the other end in your mouth and blow gentle puffs in it until a little bulb is formed. When the bulb is cold take a file and gently crack the thin glass and trim it away; now heat the tube around the edge of the hole again until the glass begins to run when a round smooth hole will be produced as shown at B.

Fig. 91A. Welding Two Tubes Together. B. Making A T Tube