Fortunately, it is comparatively easy to destroy the injurious organic impurities of water and render it wholesome for drinking purposes. This, it is true, demands a degree of care and precaution which many will not take? and as a result of ignorance and heedlessness, water is almost everywhere a common carrier of disease. The peril of injury from it can be overcome in a measure by the use of domestic filters, composed of charcoal or other substances. These, however, are much more effective in removing the mineral ingredients than the more dangerous organic particles. They also are rarely kept pure and clean, and may become simply breeding places for bacteria.
The only safe way of purifying questionable water in households is by boiling. The disease germs, whicn can endure unharmed the low temperature of liquid air, are destroyed by boiling water. To make sure, the boiling should be kept up at least ten minutes. An unpleasant effect of this is that it gives thekwater a flat taste from its loss of air. Some means should be adopted to restore to it the lost air. This may be done in a measure by subsequent filtering, the water slowly trickling down through and absorbing the air. "
of late years many cities have introduced filters on an extensive scale, to purify the total supply and thus cut off this prolific cause of disease at its source. The principal means employed for this are large filter-beds of sand and gravel, though in some cities spongy iron is used with good effect. The result has been highly encouraging in the prevention of epidemic diseases, and filter-beds are likely to be introduced before many years into the water-supply of all our larger cities.