SANITARY ESSENTIALS. 323 



der of the cistern filled with clean sand free as possible from 

 organic deposits. 



The water, collected from the roof of house or barn, perco- 

 lates through the sand to the central well, from which it may 

 be pumped. Thus filtered, it is very free from impurities, 

 is soft, clear, and potable. Such a cistern can be readily 

 cleaned, and the sanrl renewed. 



Another excellent method is to build in the same manner, 

 in form of a jug, with a manhole in the top, and a partition 

 of soft burnt bricks laid in cement separating it into two 

 compartments. The water is delivered into one, is filtered 

 through the porous brick partition into the other in a good 

 state of purity. Such a cistern should be frequently cleansed, 

 and the filtering-wall rebuilt with new bricks. 



A house forty by twenty, with a rain-fall of forty-one 

 inches, will furnish an average of sixty-five gallons a day. 

 Other methods of filtration may be used, but these are the 

 most simple, cheap, and efiicient. Rain-water stored in 

 open wood or lead-lined cisterns is often very impure, and 

 highly poisonous, — fit only for washing-purposes. 



Brook and river waters are often used. They are modified 

 in quality bj' the ground from which their waters percolatCj 

 or over which they flow, whether gravelly, marshy, or clayey. 

 They may hold in suspension or solution mineral or vege- 

 table substances, or may be quite pure and suitable for use. 

 An examination of their sources, their liability to become 

 contaminated, and their sensible properties, is usually suffi- 

 cient to determine their purity. 



The waters of ponds, either natural or artificial, if fed by 

 streams of abundant volume (unpolluted by sewage, the wash 

 of cultivated fields, and the refuse of manufactories), if rest- 

 ing on a rocky, gravelly bed, and so deep that the sun cannot 

 warm the underlying earth sufficient to cause fermentation, 

 and stimulate vegetable growth to any great amount, are as 

 pure and fit for domestic use as any that can be obtained. 



The only objection to the use of such water is its warmth 

 in summer, and consequent insipidity, which may be corrected 

 by ice, and its liability to be affected by certain vegetable 

 growths which render the water offensive to both taste and 

 smell. 



Spring-waters may be pure or impure. Their character is 



