18.  We feel objects by means of the sense of touch.

19.  The sense of touch is most acute at the tip of the tongue and the ends of the fingers.

CHAPTER XXVI.

ALCOHOL.

1. As we learned in the early part of our study of this subject, alcohol is produced by fermentation.  It is afterwards separated from water and other substances by distillation.  We will now learn a few more things about alcohol.

2.  Alcohol Burns.—­If alcohol is placed in a lamp, it will burn much like kerosene oil.  Indeed, it does not need a lamp to help it burn as does oil.  If a few drops of alcohol are placed upon a plate, it may be lighted with a match, and will burn with a pale blue flame.  Thus you see that alcohol is a sort of burning fluid.

3. The vapor of alcohol will burn also, and under some circumstances it will explode.  On this account it is better not to try any experiments with it unless some older person is close by to direct you, so that no harm may be done.  Alcohol is really a dangerous substance even though we do not take it as a drink.

4.  An Interesting Experiment.—­We have told you that all fermented drinks contain alcohol.  You will remember that wine, beer, ale, and cider are fermented drinks.  We know that these drinks contain alcohol because the chemist can separate the alcohol from the water and other substances, and thus learn just how much alcohol each contains.

5. If we should remove all the alcohol from wine, no one would care to drink it.  The same is true of beer and cider.  It is very easy to remove the alcohol by the simple process of heating.  This is the way the chemist separates it.  The heat drives the alcohol off with the steam.  If the heating is continued long enough, all the alcohol will be driven off.  The Chinaman boils his wine before drinking it.  Perhaps this is one reason why Chinamen are so seldom found drunken.

6. By a simple experiment which your parents or your teacher can perform for you, it can be readily proven that different fermented drinks contain alcohol, and also that the alcohol may be driven off by heat.  Place a basin half full of water upon the stove where it will soon boil.  Put into a glass bottle enough beer or cider so that when the bottle stands up in the basin the liquid in the bottle will be at about the same height as the water in the basin.  Now place in the neck of the bottle a closely fitting cork in which there has been inserted a piece of the stem of a clay pipe or a small glass tube.  Place the bottle in the basin.  Watch carefully until the liquid in the bottle begins to boil.  Now apply a lighted match to the end of the pipe-stem or glass tube.  Perhaps you will observe nothing at first, but continue placing the match to the pipe-stem, and pretty soon you will notice a little blue flame burning at the end of the stem.  It will go out often, but you can light it again.  This is proof that alcohol is escaping from the liquid in the bottle.  After the liquid has been boiling for some time, the flame goes out, and cannot be re-lighted, because the alcohol has been all driven off.