WHAT TO USE FOR WATER-PIPES. 139 



pipes themselves. Lime, leaves, and other sub- 

 stances, which may be deposited in the angles or 

 bends of pipes, will modify the chemical changes, so 

 as to render an otherwise safe pipe very unsafe. The 

 twisting and bending of pipes, when placed in posi- 

 tion, disturb the crystalline structure of the metal, 

 and give rise to electrical currents, which promote 

 its solution in water. Well-waters and spring- 

 waters are usually more unsuited to lead conduction 

 than those of ponds and rivers. 



As service-pipes for aqueducts, lead pipes will, 

 under ordinary conditions, deliver water free from 

 lead contamination. In a city or town supply, 

 where the general influence of the waters is protec- 

 tive, as described above, there will be local causes 

 operating, through the agency of which some fami- 

 lies will suffer from lead poison. No city or large 

 town can introduce lead service-pipes into its aque- 

 duct system, with entire exemption from danger. 

 It is not enough to learn the general influence of 

 aqueduct waters, as thereby people are misled ; we 

 must know the character of the water which flows 

 into each separate dwelling, if we would have knowl- 

 edo-e of its exact influence. If each water-taker in 



C5 



a city could have the water received carefully tested 

 twice during the first year after it is introduced, he 

 would learn whether he is free from danger or not. 

 If, after this period, the water flows pure, no anxi- 



