HOW WATER CAN BE PURIFIED 



341 



FIG. 209. As water flows over the land, it gathers filth and disease germs. 



waste matter. More than three fourths of all cases of typhoid 

 fever in the United States are caused by drinking water con- 

 taining typhoid germs, and many stomach and bowel troubles 

 are traced to contaminated water. 



It is not necessary that water should be free from all 

 foreign substances in order to be safe for drinking; a limited 

 amount of mineral matter is not injurious and may sometimes 

 be really beneficial. It is organic waste matter that causes 

 trouble, because it usually contains large numbers of disease 

 germs. 



How water can be purified. (a) Disease germs are de- 

 stroyed by strong heat, and water that has been boiled for 15 

 or 20 minutes is safe to drink. Boiling is the most practical 

 method of purification for the home. The boiled water should 

 be put into clean bottles and kept corked. The taste of boiled 



