It is perfectly safe to use kerosene in the lamp, but it gives a very smoky flame which deposits soot on the glass and fills the air with soot particles. Your mother will object very strenuously to this because the soot particles settle and blacken everything. Burn alcohol only, at least in the house. Experiment 2. To cut glass tubing. [Illustration: FIG. 7 BREAKING THE TUBE ] Cut off a six-inch length of No. 2 as follows: Lay the tube flat on the table, mark the six-inch length and draw the file across the tube at this point, pressing hard enough to make a good scratch (Fig. 6). Grasp the tube with both hands near the scratch, as in Fig. 7, pull apart and bend slightly. Do you find that the tube breaks across easily? Repeat this with No. 4 and No. 6 tubes. Experiment 3. To make the edges smooth. [Illustration: FIG. 8 MAKING THE EDGES SMOOTH ] Hold one end of the six-inch piece of No. 2 in the tip of the flame (Fig. 8), and turn constantly until it is just red hot. Take it out and let it cool on the blocks. Do you find that the edges are smooth? Repeat with the other end. Repeat with both ends of the six-inch piece of No. 4. If thick glass is heated quickly it may crack, because the hot exterior expands more quickly than the cooler interior and produces internal strains. [Illustration: FIG. 9 THE BLOWPIPE FLAME ] The No. 6 tube is comparatively thick and should be heated =gradually= as follows: Hold the end in the flame for about 1 second, then withdraw it for about 1 second; hold it in the flame again for 1 second, and withdraw it for 1 second. Repeat this eight or ten times, then hold and turn it in the flame until red hot. Smooth both ends of the No. 6 piece in this way. Experiment 4. Practice with the blowpipe. Hold the small end of the blowpipe just inside the flame at one edge, about ⅛ inch above the wick (Fig. 9), and blow air through the flame parallel to the top of the wick. Keep your mouth closed on the blowpipe, =breathe through your nose=, and =practice keeping a steady stream of air going for a long time=. You will be able to do this with a little practice. Do you observe that the blowpipe flame is pointed, also that it is made up of a pointed cone inside and a lighter-colored cone outside? The hottest part of the flame is inside the outer cone just beyond the point of the inner cone. [Illustration: FIG. 10 CLOSING ONE END OF A TUBE ] The blowpipe flame is hotter than the lamp flame because the heat of the burning alcohol is concentrated at one point by means of the air blast, and because the alcohol is more completely burned by the extra air. Experiment 5. To close the end of a small tube. Hold one end of a piece of No. 2 tube in the blowpipe flame (Fig. 10), turn it slowly, and heat until the end closes. Does it close nicely? Close one end of a piece of No. 4 in the same way.