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with hydrosulphuric acid and oxide of tin are both represented in the numbers below.

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0.100 0.100 0.000 0.000
0.020 | 0.010 0.000 0.000 0.100
0.010 0.010 0.000 0.000 0.000
0.001 0.000 0.000 0.000 0.001
0.005 0.000 0.000 0.000 0.000
0.005 0.001 0.001 0.001 0.001 | 0.500 0.500 0.500

1.000 1.000 1.000 1.000 1.000 0.050 / 2.000 / 2.000 26 8.000 15.000 10.000 8.000 0.010 | 0.000 50.000 0.010

10.000 25.000 8.000 10.000 3.000 7.000 1.000 10.000 | 75 | 10.000 15.000 15.000 110.000 4.000 4.000 / 7.000 / 20.000

“ The action in ten days' exposure was inconsiderable. No coat formed on the tin.

“A portion of Cochituate water that had been standing two months in tin pipe, which was kindly furnished last February by the engineer of the water-works, was evaporated to dryness with carbonate of soda, and gave with the blowpipe a malleable metallic button. The precip. itated oxide from this water, that from distilled water acting upon chemically pure tin, and that from Cochituate and the various other waters upon the impure tin, were identical in appearance.

“Lehman remarks of the solubility of tin in solutions of sal-ammoniac, alum, and bisulphate and bitartrate of potassa.* • Lindes has examined the solutions which by boiling attack tin vessels. According to his experiments, tin is rapidly brought into solution, without precipitating the oxide by alum, sal-ammoniac, and bisulphate of potassa. Without dissolving the oxide, but merely depositing it, chlorides of barium and calcium, neutral carbonate and bicarbonate of potassa, sulphates of potassa, soda, and magnesia, chloride of sodium, tartrates of ammonia and potassa, and borate of potassa.' † These experiments were made with the aid of heat. Time accomplished the same end in all the waters I have employed, including distilled water, producing either solution or deposit of the oxide, not upon the tin, but the bottom of the containing vessel. Lindes did not observe that saltpetre acted with the aid of elevated temperature. The time in his experiments

* Taschenbuch der Chemie, 1848, S. 192. | Berzelius, Jahresbericht, Vol. XII., S. 110, 1833.

was probably too short, as I have found that tin at common temperatures yields the insoluble oxide in a solution of saltpetre.

“ TABLE XXVII. — Experiments with Tinned Copper Pipe.* — Two days' exposure. 100cc. condensed to 5cc. |DayaDistilled c he Croton. Jamaica. Fairmount. Albany.

Cambridge Hard Water.

| 2 | 15 000 20.000 10.000 20.000 / 20.000 20.000 20.000

“Upon the authority of Dr. Hayes t I have ventured to speak of the safe use of tinned copper pipes, notwithstanding the fact of the slow erosion.

Iron service-pipes, such as are employed for the circulation of hot water and steam, for warming purposes, have been proposed, and are in use. I am informed that some persons who laid them down a few months since for the distribution of Cochituate water have decided to replace them with lead, on account of the rust, which unfits the water for washing.

“Iron pipes tinned within and without have been submitted to me. I have no knowledge of the durability of the coat of tin. Should it prove to be lasting, this pipe will have the double advantage of the strength of iron and the feeble action which tin experiences.

“ A pipe consisting of gutta percha and India rubber was found to yield an extract to water, which gradually diminished, until the taste was no longer impaired. The strength of the specimen submitted to me was not sufficient to sustain the pressure of actual service.

“ Pipes of pure gutta percha have been proposed by Dr. Webster, and, from all the experiments I have been able to make, as well as from the known chemical properties of the substance, I shall not be surprised to find that they may be successfully introduced into wells. Its susceptibility to extension when heated, if only to the temperature of boiling water, precludes its use for some of the purposes of servicepipes.

Glass pipes have been used for the transmission of water, where the descent was moderate, and the head inconsiderable. Where the pressure is sufficient to supply the upper rooms of houses, practice has

* The pipe, five eighths of an inch in diameter, was washed with warm diluted hydrochloric acid, then with warm diluted potassa, then with distilled water, and then successively exposed to the different waters mentioned above. | Report to the Board of Consulting Physicians, Boston, 1848.. VOL. II.

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shown that the pipes are liable to be shattered by the concussion occasioned by shutting off 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. Open waters, derived from rain-falls and surface drainage, like ponds, lakes, rivers, and some springs ; and 2. Waters concealed from sunlight, and supplied by lixiviation through soils or rock, or both, 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 percentage 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 inverted, in high latitudes for a longer, and in lower latitudes for a shorter 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 (.) 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 quantity, 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.

" (F.) 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 animalculæ 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 pulverulent peroxide of iron may influence it.

" (h.) Alkaline chlorides in natural waters deprived of air do not cor. rode lead. (i.) 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 oxide, 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 (l.) 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 Distribution-pipes may be 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.

(6.) In experiments with Croton, Fairmount, Jamaica, and Cochituate 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 suffer 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 process of time, impermeable to and insoluble in the water in which it occurs.”

Lieutenant C. H. Davis, U. S. N., presented a paper upon the “ Geological Action of the Tidal and other Currents of the Ocean.”

“ The object of this memoir,” he said, " is to present the subject of the tides and currents of the ocean as a geological problem. The tides have heretofore been regarded only as an astronomical problem. It is the prevailing opinion among geologists, at present, that the actual condition of the earth and the changes of former periods are to be ascribed to causes now in operation. Among the present active causes of change, the ocean holds a prominent place. But it has been supposed to operate principally by means of the agitations of its surface, or by violent and tumultuous disturbances. The tides and currents of the sea have been treated in a general way only. This memoir announces the discovery of a permanent, systematic, and uniform relation between the tidal currents and those shores which are now, or have been at any earlier period, subjected to their action. The currents created by the tides are to be counted among the most effective agents employed throughout all periods in giving their present form and body to the great continents, and in preparing a suitable home for that marine animal life of which there is such an enormous display in the fossils of earlier strata, and which constitutes at present an important part of the sustenance of man.

“ If this agency be established, the whole economy of the earth's condition will appear to be connected with the normal and regular movements of the ocean, rather than with its violent and irregular action. The title of the Geological Action of the Tides does not exclude the consideration of those currents of the ocean produced by other causes, which exert an influence by coming in contact with the land. But these currents hold a subordinate place to the tides. They owe their existence and direction, in part, to the continents, and move always in the same course. But the tides have contributed largely in giving their present forms to the continents, and are themselves constantly undergoing alternate changes of rest and motion, flux and reflux, by which they are peculiarly qualified for their office of distribution and construction. The view now presented will account for the alluvial deposits on this coast, and for similar sandy formations elsewhere, as in Holland, the Landes of France, Northern Peru, &c. It will explain the geological peculiarities of the great plains of North

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