=71. Root beer.=--Some persons boil roots and herbs, and add molasses and yeast. Then the liquid ferments and becomes _root beer_. They say "it has no alcohol, for we made it." But it does have alcohol, for yeast always makes alcohol. Some ginger ale is made by putting yeast in sweetened ginger water. It has alcohol, too. =72. Distillation.=--Boiling water turns to vapor or steam and goes off in the air. When the vapor is cooled, you can see the water again. It often cools on the window and makes little streams of water. You can catch the steam in a tube. If you keep the tube cool, the steam will turn to water in the tube. This process is called _distillation_. [Illustration: =A glass of whisky contains so much alcohol.=] Boiling alcohol also passes off into the air as vapor. When the vapor is cooled, it becomes liquid again. Alcohol boils with less heat than water. When alcohol in water is heated, the alcohol boils first. So the vapor has more alcohol than the water. When the vapor is cooled, the liquid has more alcohol than it had at first. When the liquid is distilled again it has more alcohol yet. Pure alcohol can be made in this way. =73. Whisky.=--Distilling wine or strong beer makes _whisky_ and _brandy_. Whisky is one half alcohol. It is more harmful than wine or beer. =74. Habit.=--Some strong drinks have only a little alcohol and some have a great deal. No one begins to drink the strong liquors. He begins with wine or beer. When he has once learned, he has a hard time to stop drinking. It is dangerous to drink even weak drinks. =75. Strong drink and thirst.=--When a man is thirsty, water will satisfy him but strong drink will not. Sometimes the mouth is dry and dirty and then a man feels thirsty. Rinsing the mouth with water, and rubbing the tongue and teeth clean will help the dryness and stop the thirst. At any rate, strong drink will only make the mouth dryer. Some men drink only when they are tired. Then a cup of strong and hot tea or coffee will make them feel much better than a glass of strong drink, and will not harm them so much. When strong drink is swallowed, its alcohol takes water from the mouth. When your mouth is dry, you feel thirsty. Strong drink makes the mouth dry, and so a drink makes a man more thirsty. The alcohol also makes the mouth smart. Men need another drink to cool the mouth after the first one. So one drink leads to another. All the while a person drinks water with the alcohol until he has too much water. But his mouth is dry and he feels as thirsty as ever. =76. Effect of alcohol upon the stomach.=--When strong drink is swallowed it makes the stomach smart just as it does the mouth. So the stomach feels warm, but it is really no warmer. This harms the stomach and keeps it from working well. Alcohol also keeps the gastric juice from changing albumin to a liquid. Alcohol keeps flesh from decaying in a museum. In the same way it may hinder the digestion of food in the stomach.