In 12 ounces of distilled water, contained in a shallow glass basin, loosely covered to exclude the dust, twelve

brightly polished lead rods weighing 340 grains, will lose 2J grains in 8 days, and the lead will show evident marks of corrosion ; and this action will go on as long as

the water is exposed to the air. While these changes are going on, a small quantity of lead will be dissolved, as may be shown by carefully filtering the water acidulating

with a drop or two of nitric acid, and evaporating to dryness. Sulphuretted hydrogen is also a good test, occasioning, where lead is present, first a brown color, and subsequently a black precipitate. Christison has proved that the lead which is dissolved, is in the form of the carbonate, and hydrate of the oxide, or, oxide of lead, carbonic acid and water. The fact is then sufficiently established, that distilled water has the property of dissolving lead -- Does the same hold true in relation to waters in ordinary use 1 In the year 1809, it was first announced by Guyton Morveau, that the salts which are held in solution by some natural waters, destroy their property of acting on lead, and

that of these modifying circumstances none are more remarkable in their action

than the neutral salts. Dr. Christison has pursued this investigation with great success, and has proved that this preservative power exists in the case of sulphates,

muriates, carbonates, hydriodates, phosphates, nitrates, acetates, tartrates, arsenates, &c. These salts, however, do not possess an equally protective influence, the carbonates and sulphates being most, the chlorides the least energetic of those saline substances commonly met with in waters. As a general rule, it appears that those whose acid forms with the lead a soluble salt of lead, are the least energetic ; while those whose acid forms an insoluble salt of lead, are most energetic.