CHAPTER XII.
WATER SUPPLY: QUALITIES OF WATER, INFLUENCE ON HEALTH; WASHING, COOKING, &c.
75. The goodness of the water used by us is of very great importance. Many more diseases are caused by bad water than even by bad food. Water forms three-quarters of our weight, and before any part of our food can be taken into our bodies it must be dissolved in the watery fluids of the stomach. All fresh vegetables contain a very large proportion of water. Thus potatoes consist of three-quarters, and turnips, and cabbage of upwards of nine-tenths, of their weight of this liquid. Even the driest vegetable substances contain a large proportion. Dry wheaten flour has fifteen pounds of water in every hundred; this is driven off by the heat when it is baked in making infant's food;¹ and bread contains one third of its weight of water.
76. Water has so great a power of dissolving other substances, that it is not found anywhere in a perfectly pure state, but has always in it mineral substances, sometimes decaying vegetable and even animal materials derived from the soil or earth through which it flows, and gases and odours absorbed from the air.
¹ See Appendix, First Lesson.
77. In large towns water is usually supplied by the water companies through pipes, having been obtained from rivers. The water is generally supplied only for a short time each day, and the quantity received has to be stored up in cisterns or water-butts. These should be every frequently cleaned out, as the impurities of the water settle at the bottom and are stirred up each time the fresh water comes in. Water-butts and cisterns should never be placed near any decaying matters, such as manure heaps, or in close underground cellars, or near cesspools or drains, as the water very quickly absorbs the gases and bad smells arising from such substances, and becomes unwholesome. Water standing for a night in a close or crowded room absorbs the impure air and becoems unpleasant to the taste and injurious to health. When the waste or overflow pipe from a cistern runs into a drain the foul air rises up the pipe and renders the water unwholesome, and the same evil arises if the cistern supplies a water-closet.
78. River water varies very much in quality, that from some rivers contains a great amount of decaying matter from the sewers and drains that run into them; such water should not be used if it is possible to avoid it, but if no other can be obtained, it should be filtered and boiled before being drunk, or used in preparing food.
All river water contains a small proportion of chalk, or carbonate of lime, dissolved in it. If the quantity is large the water is said to be hard—the greater the proportion of chalk the harder the water. The water of the river Thames, with which the greater part of London is supplied, contains fourteen grains of chalk