To fix the description, suppose it is desired to join two tubes (see Fig. 8), each about one inch in diameter and a yard long. Get four clip stands and place them on a level table. Be sure that the stands are firm and have not warped so as to rock. In each pair of clips place a tube, so that the two tubes are at the same height from the table, and, in fact, exactly abut, with axes in the same straight line. Close one tube by a cork and then fix the blowing apparatus as shown to the other. In such an operation as this the drying apparatus may be dispensed with, and a rubber tube simply connected to one end of the system and brought to the mouth. Take the oxygen blow-pipe and turn the nozzle till the flame issues towards you, and see that the flame is in order. Then turn down the oxygen till it only suffices to clear the smoky flame, and commence to heat the proposed joint by a current of hot air, moving the flame round the joint. Finally, bring to bear the most powerful flame you can get out of the blow-pipe, and carry it round the joint so quickly that you have the latter all hot at once. Put down the blow-pipe, and, using both hands, press the tubes together (which wooden clips will readily allow), and after seeing that the glass has touched everywhere, pull the tubes a trifle apart. Apply the blow-pipe again, passing lightly over the thin parts, if any, and heating thicker ones; having the end of the rubber tube in his mouth, the operator will be able to blow out thick places. When all is hot, blow out slightly, and having taken the flame away, pull the tubes a little apart, and see that they are straight. Throw an asbestos rag over the joint, loosen one pair of the clamps slightly, and leave the joint to anneal. It is important that the least possible amount of glass should be heated, hence the necessity of having the ends well prepared, and it is also important that the work should be done quickly; otherwise glass will flow from the upper side downwards and no strong joint will be obtained. Fig. 17. Tube being opened at one end. Sec. 24. To weld Tubes of very small Bore. If the bore is not so small as to prevent the entrance of the point of the iron nail, get the ends of the tubes hot, and open the bore by inserting the end of the nail previously smeared over with a trace of vaseline. Work the nail round by holding the handle between the thumb and first finger of the right hand, the tube being similarly placed in the left. The tube and nail should be inclined as shown in the sketch.