A drink of water taken the first thing in the morning tends to clean out the digestive tract and put one in good condition for breakfast. Water with meals aids digestion, provided it is not used to wash down food but is taken when the mouth is empty. It should not be extremely cold nor hot. Two glasses at a single meal are usually all that are desirable. When there is much water in the food, as in soups, milk, fruits, and some vegetables, or when other beverages are taken, less will be taken as plain water. When one feels hungry and uncomfortable between meals a drink of water will often relieve the sensation. Water is either _soft_ or _hard_. Rain water is perfectly soft, but as it passes through the earth after falling, it sometimes becomes laden with mineral substances, that affect its cleansing properties, and that may affect its physiological action. Such water is called _hard_. _Temporary hardness_ is caused by a soluble lime compound which is precipitated by boiling. If the teakettle is incrusted inside by a layer of lime, the hardness is of this character. Such water should be boiled and cooled for drinking. _Permanent hardness_ is due to other compounds of lime and magnesia which are not precipitated by boiling, but which can be counteracted for cleansing purposes by the addition of some substance like ammonia, borax, or soda. If the excess of salts has some undesirable physiological effect, this water should be distilled, or bottled water for drinking brought from elsewhere. Of much greater importance is the question of the freedom of the water supply from harmful bacteria and organic matter. Never use a well without having the water tested by an expert. This will sometimes be done by the local or state Board of Health or Experiment Station. All water sources should be guarded from contamination. (See “Shelter and Clothing,” Chapter V.) Filters may be used, and are effective in straining out sediment, but the home filter is seldom to be relied upon to remove actual bacterial contamination. If used at all, the filter should be frequently cleaned and sterilized in boiling water. In case the supply is suspected, the water for drinking should be boiled for at least ten minutes, allowed to settle, if necessary, and poured off into bottles for cooling. This is a practice to be commended after a heavy rainfall, and especially in the autumn. These bottles may be placed on the ice. Ice must be used with caution always in drinking water, and it is the safer way to cool the water beside the ice. The freezing of water in pond and river does not purify or sterilize it. Natural ice is usually questionable. Artificial ice, if properly manufactured, is much safer.