OF ARTS AND SCIENCES. 99 



" (h.) Alkaline chlorides in natural waters deprived of air do not cor- 

 rode lead. {(.) Salts, generally, impair the action of waters upon lead, 

 by lessening their solvent power for air, and by lessening their solvent 

 power for other salts. A coat of greater or less permeability forms in 

 all natural waters to which lead is exposed. The first coat (j.) is a 

 simple suboxide absolutely insoluble in water, and solutions of salts 

 generally. This becomes converted in some waters into a higher ox- 

 ide, and this higher oxide, uniting with water and carbonic acid, forms 

 a coat {k.) soluble in from 7,000 to 10,000 times its weight of pure 

 water. The above oxide unites with sulphuric and other acids which 

 sometimes enter into the constitution of the coat k ; — uniting with or- 

 ganic matter and iron-rust, it forms another coat(Z.) which is in the 

 highest degree protective. The perfection of this coat, and of the first 

 above mentioned, may be inferred from the small quantity of lead found 

 in Croton water (New York), after an exposure in pipes of from twelve 

 to thirty-six hours, and from the absence of an appreciable quantity in 

 Fairmount water (Philadelphia), after an exposure of thirty-six hours, 

 when concentrated to one two-hundredth of its bulk. 

 " Reasons why the Water of Lake Cochituate served through Iron 

 Mains and Leaden Distrihution-pipes may he safely employed as a 

 Beverage in any Form. 



" (a.) It has the small measures of air, nitrates, and chlorides, the 

 large proportion of organic matter, soluble and insoluble, and exposure 

 to the sun, above referred to as grounds of distinction in the relations 

 to lead between lake, pond, or river water, and well-water. 



" (h.) In experiments with Croton, Fairmount, Jamaica, and Cochit- 

 uate waters, made with lead, lead soldered to iron, to tin, to copper, 

 and to brass, prolonged from mid-winter to the middle of summer, the 

 relations of the last of these waters to lead were found to be as favor- 

 able as were those of either of the others. 



" (c.) Large numbers of individuals in the daily and unrestricted use 

 of Fairmount, Croton, and Jamaica waters served through lead are not 

 known by physicians of great eminence and extensive practice to suf- 

 fer in any degree from lead maladies. 



" (d.) A coat forms upon lead in Cochituate, as in the other waters 

 above mentioned, which for all practical purposes becomes, in pro- 

 cess of time, impermeable to and insoluble in the water in which 

 it occurs." 



