=Appearance.=--A drinking water should be clear and bright. When shaken in a glass or bottle, bubbles should rise quickly and break immediately. If the bubbles move slowly, or seem to hang for some time in the water, they are probably due to the presence of decaying organic matter, and the water is of questionable purity. A slight cloudiness in the appearance of the water, following a rain, may be due to the presence of a small quantity of earthy matter, and not seriously affect its wholesomeness, but if the discoloration looks like that occasioned by a drop of milk the water should be avoided until carefully tested. =Smell.=--A good water should have no smell. To this end, the cisterns or other receptacles must be kept perfectly clean. The purest and best waters will soon become foul if stored in unclean vessels. =Taste.=--Water having a disagreeable taste is apt to be unwholesome. In order that we may derive from it proper nourishment, water, like other parts of our food, should be pleasant to the taste. And yet, the taste is by no means a satisfactory test of purity. The purest of all water is distilled water, which, by reason of the absence of all mineral matter and air, has a flat and insipid taste. The cleanest rain-water is also insipid. Boiled water is not much better, for while the boiling process may have destroyed all poisonous or noxious germs, and rendered the water absolutely wholesome, it also drove off the natural gases which gave to the water a pleasant taste. Boiled water may be re-aerated by pouring from an ordinary sprinkling can several times. =Hard Water.=--Hardness is a serious drawback, whether the water be used for cooking, bathing, or for washing clothes. Food cooked by boiling in hard water is, as a rule, not so well prepared. Greens take on a gray color. Tea is never so good made from hard water. For cleaning the skin, hard water is not nearly so efficient as soft. Linens are never of a good color when washed in hard water. Boiling hard water before using it improves it. A pinch or two of carbonate of soda, or of borax, is helpful in washing. A little table salt improves it for cooking most vegetables.