the lodes reaching 50 feet, and the width of the mineral field half a mile. The underlie is small. The principal lode (the northern) has been opened on by eight pits, whence have been taken, from a depth nowhere exceeding 32 fathoms, upwards of 10,000 tons of rich copper-ore. Ore was seen at the bottom at one shaft, the lode being 35 feet wide, including about 5 feet of barren ground and some underlie on the foot wall.

2. Sykesville Copper Lodes near Baltimore, U.S.-The country here consists of metamorphic rock ranging N.N.E. and S.S.W., and dipping E.S.E. at a high angle. There are in the lodes granites, gneiss, and mica-slate, with magnesian rocks. The lodes are nearly vertical, ranging parallel to the "country", but dipping in the opposite direction. The veins at the top contain much magnetic oxide of iron, but below ten fathoms this changes to pyrites, succeeded and accompanied by copper pyrites. The lode did not appear settled at the depth reached by the existing shafts. There were several points at which pits had been sunk and some copper ore obtained: in all of them the gossan had a tendency to pass into magnetic iron-ore. A remarkable and very large group of lodes was observed at the "Point of Rocks," where the outcrop is hydrated oxide of iron, worked as an iron-ore to some extent.

3. Ducktown Copper Lodes in East Tennessee, U.S.-In the southeastern corner of Tennessee, near North Carolina and Georgia, are a number of lodes, strongly indicated by a rich gossan, and yielding a peculiar and rich black ore which has attracted much attention from American geologists. The "country" consists of altered Silurian schists, alternating with grits; all striking parallel to the mountain range (N. 30° E., S. 30° W.), and dipping S.E. at a high angle. The talcose schists pass into garnet schists and become steatitic. They are accompanied by numerous strings of quartz, not true veins, the width of which varies from a few inches to 10 or 18 feet, and which occasionally show a gossan, either of hydrous or magnetic oxide of iron, with spongy quartz. These veins are nearly parallel to the strike of the country and dip S.E.

Besides the quartz strings, and within a small tract of six square miles intersected by them, are four gossan beds, of large size but with well-defined limits, which are connected by quartz strings, as well as accompanied by solid ribs of quartz on the foot or hanging wall. These also dip S.E. The enclosing rocks are talcose and steatitic, and contain cyanite, epidote, and garnets.

The length of the gossan lodes varies from 600 yards to upwards of a mile, the breadth varying from a few yards up to 250 feet; these dimensions have been proved to be correct by measuring the outcrop of the gossan. Wherever the gossans have been sunk through, masses of black ore, highly cupriferous, have been found at a small depth (from 6 to 90 feet). Below the black ore is a hard dense quartzose veinstone spotted with copper ore, which has been worked to the depth of 18 fathoms in some places, but hitherto with no satisfactory result, although fair indications of copper lodes of the ordinary kind have been found. The thickness of the black ore

varies from a few inches to 18 feet; but, where tolerably uniform, the average is 4 or 5 feet. Rich bunches of ore are found occasionally. The ore, as assayed by Mr. Henry, consists of-sulphur, 29-47; copper, 2673; iron, 26'04; quartz, 8.6; oxygen and loss, 9-16. The yield, on an average of six samples taken carefully from heaps of ore from different mines, is 26.2 per cent. of copper.

Of the four lodes, the Hiwassee ranges N.E. and S.W., dipping S.E. about 15 inches in a fathom. The gossan has been traced for a mile and a half, the width averaging 30 feet, and the thickness of black ore 3 feet. It is continued by strings of quartz towards the S.W., and also by a kind of contra-lode, which ultimately becomes the Tennessee lode. This latter is irregular and bunchy, but has yielded large quantities of rich black ore and some red oxide. It has been traced as a gossan-lode for about three quarters of a mile, ranging N. 20° E. and S. 20° W.

The Polk-County lode is nearly parallel with the Tennessee lode, and of about the same length, as determined by its outcrop. It is associated with several veins, none of which have yet been found to be productive. Its breadth is from 20 to 40 feet, and the thickness of black ore averages 3 feet. The Isabella lode is only 600 yards long, but as much as 80 yards wide, and generally contains about 3 feet of the black ore; it ranges nearly parallel to the Hiwassee lode. It terminates abruptly, strings of quartz proceeding from the extremities, without much approach to parallelism with the productive lode.

The following are given as the points of resemblance found on comparing these lodes with others. (1) They have distinct parallel walls, and their range is independent of that of the "country." (2) They contain veinstone and show gossan. (3) They are limited in length and breadth, but apparently unlimited in depth. (4) They are parallel veins and branches. (5) They are inclined at a high angle. On the other hand they present the following differences :(1) They are generally parallel to the bedding of the enclosing schists. (2) They agree with the "country" in dip as well as in strike. (3) They contain within their walls portions of the "country" unaltered. (4) They present a mass of rich black copper ore between the gossan and veinstone, entirely distinct from either and mechanically separated. (5) The width and depth of the ore appears to bear

some relation to the form of the surface.

In some of these points of difference there is an analogy with the auriferous veins of Virginia and North Carolina, but the fourth point is peculiar. They are considered to be of the nature of stock-works, or gaping fissures filled up at a more recent date than that at which the rocks had become perfectly metamorphosed. They may be connected below with bunches of yellow copper pyrites, obtainable only by mining operations of a more regular character than have yet been undertaken. Analogous deposits are believed to occur in Virginia about 100 miles to the north.

XLIII. Intelligence and Miscellaneous Articles.

RESEARCHES ON THE ELECTRICITY OF THE AIR AND THE EARTH, AND ON THE CHEMICAL EFFECTS PRODUCED BY SLOW ACTIONS, WITH OR WITHOUT THE CONCOURSE OF ELECTRICAL FORCES. BY M. BECQUEREL.

FIRST PART. On the Electrical State of Gases and Vapours.—The

fundamental principle which must serve as a guide in researches relating to the natural sources of electricity, as also to its other sources, is this:-Every mechanical, physical, or chemical work disengages electricity; in other words, the equilibrium of the molecules cannot be disturbed without that of the electricity being so likewise. On the other hand, electricity cannot be set in motion without there being a manifestation of molecular actions, betraying themselves by an elevation of temperature, a chemical decomposition, or magnetic actions.

All combustible bodies which are conductors of electricity disengage electricity during their combustion: the combustible body sets free negative electricity, the comburant body sets free positive electricity; this fact has been placed beyond a doubt by M. Pouillet as regards charcoal. In this memoir I show that the effects are the same whether the bodies are conductors or non-conductors of electricity.

The change of the state of bodies and evaporation, properly so called, do not furnish electricity, as was long ago observed. This negative result seems to imply a contradiction to the principle indicated above, namely, that the equilibrium of the electrical forces is disturbed whenever a molecular operation is produced. Why are there no electrical effects in these cases? Would not something take place similar to what occurs in the uniform friction of two similar bodies against each other? There is no electricity, because we see no reason why one molecule should take one electricity rather than another. But if no electricity is evolved, there is a production of heat. On the other hand, we know that the friction between two similar bodies is more energetic than when they are dissimilar. We also know that changes of state are accompanied by powerful calorific effects; and besides, there appears to exist a dependence of such a nature between the production of heat and that of electricity, that when one increases, the other diminishes, and vice versa, so that one may disappear with the increase of the other. Some examples will furnish a proof of this. When electricity circulates in a metal wire, the greater the heat produced, the less the quantity of electricity passed, and vice versa; things therefore go on as though the electricity were converted into heat. When we collect the heat produced in an amalgamated couple of copper and zinc in a closed circuit, we find that the sum of heat produced in the chemical action of the acidulated water upon the zinc and in the conducting wire is constant, so that the quantity of heat disengaged in the reaction is greater in proportion as less electricity passes in the wire, and vice versa.

Have I not also proved, that in the friction of two similar bodies, effected in such a manner that one of them becomes more heated than the other, there is an evolution of electricity, and the body which becomes most heated receives the negative electricity? It has even been inferred from this, that in the friction of two dissimilar bodies, that which disengages the most heat generally has a negative tendency. All these facts show an intimate relation between the production of heat and that of electricity, which I have always regarded as concomitant, and which may be of such a nature that one becomes annulled by the increase of the other. There would therefore be nothing surprising if, in changes of condition, the electrical effects disappeared in presence of the calorific effects.

The considerations which I have just put forward support the chemical theory of the evolution of electricity in the pile; a theory which I have always maintained for more than thirty years, namely, that contact alone could not evolve electricity, and that for this purpose some molecular work is necessary.

But if the evaporation of water or of a solution in a platinum capsule at or below the temperature of ebullition furnishes no electricity, this is no longer the case if a few drops of the liquid be projected by means of a pipette into the capsule, when this is sufficiently heated to render the evaporation immediate; there is instantly a production of electricity; the vessel becomes negative to such a degree that the effect may be observed without the employment of the condenser : this effect is due to the friction of the water at the instant when it becomes converted into vapour on the inner wall of the capsule, and is of the same kind as that observed in Armstrong's experiment.

The gases are electrical at the moment when they are evolved abundantly from a liquid; hydrogen and ammonia take an excess of negative electricity; carbonic acid and oxygen an excess of positive electricity: these effects are due, not to a chemical decomposition, for then the results would be reversed, but to the friction of the gases against the liquids.

Must we not infer from this, that, by an effect of the same kind, the oxygen and carbonic acid gases exhaled from the leaves of plants carry positive electricity with them into the air?

SECOND PART. On the Electrical Effects produced by the contact of Earth and Water.—The electrical effects produced by the contact of soils with fresh and salt waters have been observed successively with plates of gold or platinum, and with the same plates covered with powdered charcoal of sugar-candy, to retard, as far as possible, the polarization produced when the circuit is closed, so as to be able to measure the effects; the charcoal then acts upon the gases deposited by its absorbent power. A sine compass was placed in the

circuit.

Numerous experiments made in the Jura, in Lorraine, in the Nivernais, and on the sea-coasts of Belgium and France, have proved that vegetable mould is always positive in its contact with fresh or sea water; that the electrical effects are very slight between waters and the adjacent soils when the latter are permeable to the waters;

thus during the inundations of the plains of the Saône, scarcely perceptible currents were obtained by establishing a metallic communication between the Saône and the soils which had just been inundated. In salt marshes, as must have been expected, the soil is negative in relation to fresh waters.

I have found that the electromotive force produced by the contact of sea-water and vegetable mould is, cæteris paribus, about 2.4 stronger than that which is produced by the contact of the same soils and fresh waters.

These experiments were followed night and day last winter at the Jardin des Plantes, by putting the water of one of the wells of the establishment in communication with the surrounding earth. Variations and inversions in the direction of the current were proved, due to the infiltration of waters containing substances, which are not always of the same nature, into the wells of large towns.

THIRD PART. On Terrestrial Couples with constant currents.-Experience having shown that the results could only be depended upon when the electrodes prepared with charcoal had been placed for several days in contact with the soils and waters, I found myself compelled in the course of last summer to establish an observatory in a locality of the department of Loiret, where I collected a great part of the materials contained in the memoir which I now present to the Academy.

On comparing the terrestrial couple composed of salt water of 3o, good vegetable mould, and two coke electrodes, with a couple with sulphate of copper, it was found that the electromotive force obtained with sea-water or salt water is 0.45 of that of the latter couple; this consisted of a glass vessel containing a saturated solution of sulphate of copper and a plate of copper, and of an immersed diaphragm of unglazed porcelain containing water acidulated with one-tenth of sulphuric acid, and a cylinder of amalgamated zinc. By employing as electrodes, coke covered with peroxide of manganese, this force becomes five times as great; the peroxide of manganese acts by removing the hydrogen which is deposited on the negative electrode, which causes a current in the same direction as the terrestrial current. The electromotive force at the contact of water and vegetable mould is the tenth of that of the couple formed of amalgamated zinc immersed in fresh water and charcoal in contact with vegetable mould.

The composite terrestrial couple, formed of salt water of 3° in which a plate of amalgamated zinc is immersed, and of vegetable mould in contact with a plate of manganized charcoal, has an electromotive force represented by 0.52, that of the couple with sulphate of copper being represented by 0.579, and that of the couple with nitric acid by 10. This couple was that of Grove, formed of a dia. phragm of 4 centims. in length and 2 in diameter, and an electrode of platinum 4 centims. in length and breadth. The diaphragm contained acidulated water (one-tenth) in which a little cylinder of amalgamated zinc was immersed.

The constancy of the current of this composite terrestrial couple