It must be well known to chemists, that when solution of acetate of lead is added to the transparent and colourless water of springs, wells, and rivers, a more or less dense white cloud is almost invariably produced. This reaction has been usually attributed to the presence of inorganic salts, such as carbonates, sulphates, and muriates; but it will be found that, generally speaking, this precipitate is formed even after the water has been boiled; that it is usually dissolved by the speedy addition of a drop or two either of acetic or of nitric acid, without visible effervescence; and that the agency of the water with nitrate of silver is commonly too small to admit of its being caused by any muriate.