Water plays a very important part in this world of ours. It is encountered in minerals as a chemical constituent. It enters very largely into the composition of and things of vegetable growth, from the blade of grass to the sturdy oak. Many vegetables, as cabbage, potatoes, celery, lettuce, etc., are composed largely of water. Fruit also contains a large amount of water. The bodies of all animals contain much water. If the water could all be removed from a human body, a very small weight would balance what is left. Since fruits and vegetables, as well as animal foods, are composed so largely of water, a human being takes much water in his food, and this is the same as other water, so far as its work in the body is concerned. Water is taken in also with the air which is breathed. A body composed so largely of water as is that of the human being needs much more water than the food and air supply. Much is needed to enable the body to perform its necessary functions, and the skin must be kept clean to aid the internal organs in their ceaseless and worthy efforts to excrete watery solutions and keep the person in good health.
Nature has supplied this universal solvent very plentifully, and distributed it over much of the earth's surface, and under some portions of it. Water for the nourishment of men and animals is derived largely from rain water stored in cisterns, etc., and from springs, lakes, rivers, and wells. The term "rain water" is applied to the water which reaches us from the clouds, direct, whether in the form of rain, hail, or snow. Rain water should be allowed to fall a sufficient length of time to wash the dust particles and other impurities from the air, and the smoke and dust from the roof, before it is allowed to enter the cistern. A cistern should be walled with material practically insoluble in water, and well cemented. It should be kept well covered, to prevent the entrance of all impurities.
Rain or melting snow is the usual source of spring water. The water sinks into the earth, and percolates through layer after layer, until it reaches- an impervious stratum of rock or clay. There it rests until the accumulation is so great that it must have more room. It then breaks through the soil at some lower level in the form of a spring. Rivers usually have their source in a lake situated among the mountains, or on other high land. These lakes receive the water from the melting snows on the surrounding heights, and from the rainfall, as well as that which seeps through the rocks. When the lake basin can hold no more water, a tiny stream flows out over the lower land, and receives similar streams and large rivers until, when it reaches the sea, there is a large amount of water. Lakes are formed by melting snow and rain, which flow in small streams into a basin having a bottom impervious to water. Wells are artificial openings into underground water, and are of three kinds. Shallow wells from fifteen to fifty feet are dug, and walled with brick or stone. These are fed by surface water, and are often visibily affected by copious rainfall or protracted drouth. Driven wells are deeper, and often pass through a layer of some material which is impervious to water. Artesian wells are sometimes of very great depth, ranging from some hundreds to a few thousand feet deep.