upon the liquid which surrounds it, and with which it mingles. There are thus (including chemical action), four causes which concur in the production of the electrical effects, of which the result is shewn by the galvanometer. The action of saline solutions upon each other, or upon acids, being often one of the preponderating causes, when the chemical action is feeble, it is upon its examination that M. Becquerel first enters. He then gives an easy means of observing the electrical effect which results from the action of an acid or a liquid upon a metal, the reaction of liquids not being considered. The author then examines the effects which take place in a voltaic element, in consequence of the chemical action of liquids on each of the metals. To appreciate these effects, he takes a glass vessel, in the interior of which he places two leather partitions, to retard the mixture of the liquids contained in each of the cases. On trying different liquids, it is found that the maximum of intensity of the current takes place perceptibly when copper is immersed in a saturated solution of nitrate of copper, and zinc in a sa turated solution of sulphate of zinc. From this he deduces a process for having in a voltaic couple electrical effects which exhibit very little variation during an hour. Several voltaic couples united lead to the same result. The electrical forces developed in the chemical action of liquids have been employed by M. Becquerel to produce combinations. Carbon, which is one of the most extensively diffused simple bodies in nature, and which performs a conspicuous part in its phenomena, is first submitted to investigation. The property which this body possesses of combining in various proportions with hydrogen, has enabled him to form chlorurets and insoluble metallic iodurets, If, for example, some hydrochloric acid, a plate of silver and carbon, are put into a tube, the silver being positive, the pole attracts the chlorine, with which it forms chloruret of silver, which crystallizes in octahedrons; the hydrogen prevails over the carbon, combines with it, and the gaseous product is disengaged. To form double chlorurets and double iodurets, a tube is taken, bent in the form of the letter V, and filled at its lower part with sand or clay impregnated with water. A solution of nitrate of copper is poured into one of the branches, and into the other a solution of an alkaline or earthy hydrochlorate. The communication is then established with a plate of copper. The end,

immersed in the nitrate solution, and which is the positive pole of the pile, becomes covered with copper in the metallic state; the nitric acid remains in the solution, and the oxygen alone goes to the other end to oxidize the metal. There are then formed on this side crystals of double chloruret. These crystals have been carefully analyzed. The hydrochlorates of ammonia, lime, potash, barytes, &c. yield, with oxichloruret of copper, crystals which belong to the same system of crystallization, and these salts have precisely the same atomic composition. This result affords a verification to the law discovered by Mitscherlich. Other metals were substituted for copper, and the solutions changed. At the first moments of crystallization, the crystal is complete; but, when the apparatus has wrought for a long time, truncations begin to appear on the angles and edges. To obtain the metallic oxides crystallized, another method is adopted. For the protoxide of copper, for example, there is poured into a tube a solution of nitrate of copper, in the bottom of which is placed deutoxide of copper; a plate of copper is then immersed in it; cubical crystals of protoxide of copper gradually form on the part of the plate which does not touch the deutoxide. The action which determines the formation of this substance has been developed with much detail, as well as the various circumstances which accompany it. The influence of light and the earth's magnetism are sometimes remarked in the above mentioned effects, notwithstanding its feeble intensity. M. Becquerel related an experiment which leaves no doubt on this subject. The author mentioned that the facts exposed in his memoir were the result of two years' experiments.

2. Metallic Electricity.-M. Auguste Delarive of Geneva, has constantly observed, that the action produced by the elements of a pile ceases completely when these elements are placed either in a vacuum or in a medium which exercises no chemical action upon them. On the other hand, M. Delarive has repeated with success the experiments of an English chemist, who produced electricity by means of a pile composed solely of zinc. Of the two surfaces of each plate, the one is rough and the other polished. These plates, which, when placed at a distance from one another, only communicate by means of the ambient air, yet develope an appreciable electricity even with

out the assistance of the condenser. The consequences which result from these two series of experiments, with respect to the idea to be formed of the principal cause of the development of electricity in the pile, are evident, and appear to us to be of a nature to modify the ideas of the learned world respecting one of the most important facts in natural philosophy.

3. Influence of Meteorological Phenomena on Dry Piles.M. Donné lately read to the Academy of Sciences, a memoir, entitled Inquiries respecting the Influences which Meteorological Phenomena exercise on Dry Piles. The dry piles invented by M. Zamboni had not hitherto been sufficiently studied with reference to the variations which their tension undergoes from the influence of meteorological phenomena. It was therefore of importance to determine, by experiments directed toward this object, what is the particular action of humidity, temperature, atmospheric weight, and electricity, upon that instrument, and then to observe it during a long period when under the influence of all these causes together. The first part of this memoir comprehends the result of these experiments: in the second it is inquired whether the dry piles may be compared to the voltaic pile, and if it is possible to make it produce some chemical action.-Humidity. Humid air acts only as a conducting body, by carrying off more or less electricity, and not by modifying the function of the pile.—Atmospheric weight. There is no relation between the variations of tension of the dry piles and the barometric heights. If a pile is placed under the bell of a pneumatic machine, and a vacuum is made, it experiences no diminution in its tension, even when the vacuum is kept up as exactly as possible for several days. This is in contradiction to the well known experiment, which tends to prove that air is necessary for forcing the electric fluid into the conductors; but the fact is constant, and has been verified by repeated experiments.-Temperature. Of all the atmospherical circumstances this acts in the most diversified and most immediate manner upon the dry piles, and its action is extremely complicated. In fact, experiment and observation have demonstrated, 1st, That its effects are different according as the variations are quick and instantaneous, or take place slowly and progressively. In the former case, the tension of the pile is considerably dimi

nished, and may even be reduced to 0°; in the latter, this action is much more moderate. 2dly, Temperature acts mechanically in dilating or contracting the pile, and consequently in augmenting its energy by the greater pressure which the ele ments undergo when the pile elongates, or in diminishing it, when the contrary effect takes place. It also acts upon the function of the pile, by favouring the chemical action which electricity produces. 3dly, Temperature does not produce its effects suddenly, but only after a certain time. It does not act in an absolute manner; in other words, such a degree of tension does not answer to such a degree of the thermometer, but its action has relation to the temperature which has existed some hours before. 4thly, Heat frequently only increases the rapi dity of the current, and not the quantity of the electricity produced.-Atmospheric Electricity. The question whether the electric state of the air and the other meteorological phenomena have a direct influence upon the tension of dry piles, is undoubtedly the most interesting and the most difficult to be sol ved. It is evident that the causes hitherto preferred are incapable of accounting for all the variations that are observed in the tension of the piles. It is in the electrical influences then that we are to seek the explanation of the anomalies which their action presents? On this subject experiment gives the following results: If, by means of the electric machine, positive electricity is made to arrive at the negative pole, the tension augments considerably at the positive pole, while, if it is at the positive pole that positive electricity is made to arrive, the tension is reduced to 0° at the negative pole. In a word, electricity arriving at the pole of the same name, reduces the tension of the other pole, and electricity arriving at the pole of the contrary name, augments the tension of the other pole. Now, the piles which are observed being commonly placed under a glass globe, and communicating by one pole with the reservoir, and the other being isolated in a medium little accessible to humidity, it is not therefore to the latter that the electricity can be transmitted, and its action can only be conceived by supposing that it comes from the earth. But does it not in fact happen, that when an electric cloud approaches the earth, a certain quantity of the natural fluid of the common reservoir is decomposed, and at

tracted by the opposite electricity?

The earth's surface must

thus present, at the place where a thunder-storm exists, a positive or negative fluid, which recomposes itself with the electricity of the clouds, when the rain furnishes it with a conductor. This fact may be verified by direct experiment, since it is sufficient, during a thunder-storm, to put a very sensible electrometer in connexion with the common reservoir, to obtain signs of electricity. It is true, that it is not during thunder-storms that the great changes take place in the variations of the tension of dry piles. But is it not possible that there may be thunder-storms in the bowels of the earth, as there are in the atmosphere? That in earthquakes especially, great decompositions of electric fluid take place, which respond at great distances, and which act upon our instruments much more powerfully than the thunder-storms of our atmosphere! But it will always be very difficult to arrive, in this matter, at a sure result, seeing it is impossible for us to know how the electric fluid is propagated and distributed in the strata of the earth, which are so diversified, and since an effect which is produced here may be very imperceptible elsewhere, besides that it must often happen that the effects of temperature are confounded with others. It appears demonstrated, however, that the earth being capable of furnishing electricity to the dry piles in certain cases, their tension may be augmented or diminished. May Zamboni's apparatus produce some chemical action, and may its action be compared to that of the Voltaic pile? A string formed of fifty-two dry piles, of a thousand plates each, gave strong sparks, but its chemical action was absolutely null. It was even impossible, by employing Wollaston's method, to decompose water, or change the colour of the weakest tinctures. It is not here that force is wanting to act chemically upon the bodies; it is that there is no current in the dry piles, as is understood to be the case with Voltaic electricity: their action is entirely that of tension, and not at all galvanic. To form a proper idea of the dry piles, they must not be compared to the Voltaic pile, but to an electrical machine, which is recharged of itself. The current which it produces is but a series of discharges, a series of sparks which follow each other, at very short intervals, and which, for this very reason, cannot produce any chemical effect.