98 PROCEEDINGS OF THE AMERICAN ACADEMY 



shown that the pipes are liable to be shattered by the concussion oc- 

 casioned by shutting oft' the water. 



" Summary of Conclusions relating to the Different Kinds 

 OF Water and Leaden Service-pipe. — The waters used by man, in 

 the various forms of beverage and for culinary purposes, are of two 

 classes, viz. : — 



" 1. Ojjen waters, derived from rain-falls and surface draiiiage, 

 like ponds, lakes, rivers, and some springs ; and 2. Waters concealed 

 from sunlight, and supplied by lixivialion through soils or rock, or 

 loth, of greater or less depth, such as wells and certain springs. 



" They differ, (a.) in temperature ; well-water, through a large part 

 of the year, is colder than lake, pond, or river water; — (b.) in the per- 

 centage of gases in solution ; recently drawn well-water, in summer 

 particularly, parts with a quantity of air upon exposure to the surface 

 temperature. In winter these relationships must to some extent be in- 

 verted, in high latitudes for a longer, and in lower latitudes for a short- 

 er period, (c.) They differ in the percentage of inorganic matter in 

 solution ; well-waters contain more ; — (d.) in the relative proportions 

 of salts in solution ; well-waters contain more nitrates and chlorides ; — 

 and (e.) in the percentage of organic matter; well-waters contain less. 



" Relations of Lead to Air and Water. — (a.) Lead is not oxidated 

 in dry air, or (b.) in pure water deprived of air. (c.) It is oxidated in 

 water, other things being equal, in general proportion to the amount of 

 uncombined oxygen in solution, {d.) When present in sufficient quan- 

 tity, nitrates in neutral waters are, to some extent, reduced by lead. 

 (e.) Both nitrates and chlorides promote the solution of some coats 

 formed on lead. 



" if) Organic matter influences the action of water upon lead. If 

 insoluble, it impairs the action by facilitating the escape of air ; if sol- 

 uble, by consuming the oxygen in solution, and by reducing the nitrates 

 when present. The green plants, so called, and animalcule which 

 evolve oxygen, are abundant in open waters in warm weather only, 

 and of course when the capacity of water to retain air in solution is 

 lowest ; so that, although oxygen is produced in open waters by these 

 microscopic organisms, it does not increase the vigor of their action 

 upon lead. 



" (g.) Hydrated peroxide of iron (iron-rust) in water is not reduced 

 by lead. Hence may be inferred the freedom from corrosion of leaden 

 pipes connected with iron mains, so far as the reduction of the pulver- 

 ulent peroxide of iron may influence it. 



