counts for the Heat evolved by the Combustion of certain bodies on the hypothesis of its arising from resistance to the conduction of electricity between oxygen and the combustibles, at the moment of their union. Taking this view of the phenomena, he shows that the heat evolved by the union of the atoms is in proportion to the electromotive force of the current passing between them-in other words, to the intensity of their chemical affinity. Mr. Joule instanced copper, and explained the manner in which he had obtained the theoretical results for it. He alluded, in passing, to the fact, that pure water is not at all decomposed by ten pairs of Smee's battery in series; the current being thereby almost, if not quite, cut off. A diagram gave the quantities converted into protoxides of potassium, zinc, iron, copper, and hydrogen, with Dulong's results and his own in parallel columns. Another column gave the theoretical results, and another the corrected theoretical results, which latter agreed very nearly with the experiments of Dulong and the author. An extensive series of experiments conducted by Mr. Joule seemed to indicate that heat is lost when light is evolved; but in so slight a degree, that his experiments on the heat of combustion needed not to be corrected for it.

To sum up the correctness of the idea first stated by Davy, and supported by Berzelius, that the heat of combustion is an electrical phenomenon, is now rendered sufficiently evident; as well as that the heat arises from resistance to the conduction of electricity between the atoms of combustibles and oxygen at the moment of their union. Of the nature of this resistance we are still ignorant.

PHENOMENA OF CHEMICAL INDUCTION.

M. ARAGO has detailed to the Academy of Sciences, at Paris, two memoirs, by Mr. Dove, "On the Phenomena of Chemical Induction." An electrical current causes, in a mass of iron placed near it, two kinds of phenomena―one corresponding to magnetism, the other to dynamical electricity. The author of these memoirs announced that he had succeeded in separating the two classes of action, by giving them different degrees of relative intensity; and that he had shown the magnetic action to exist in substances where its presence had not been suspected.

CIRCULAR POLARIZATION APPLIED TO CHEMICAL INQUIRIES. PROF. POWELL has detailed to the British Association, an account of a Simplified Apparatus, for applying Circular Polarization to Chemical Inquiries. The application of the phenomena of circular polarization in characterizing certain liquid solutions, was fully pointed out by Biot, who also contrived a very accurate apparatus for examining the effects in question. But that apparatus being expensive and difficult of adjustment, Prof. Powell has devised a simpler instrument, sufficiently accurate for general indications, and for the objects of the chemical student. He places the solution to be examined in a common test tube, which must, of course, be fixed in a vertical position; below the tube is the polarizing plate making with it an angle of 350,

and above it is a double refracting crystal, (rhomboidal calcareous spar,) in its natural state. The light is thrown on the polarizing plate by a plane mirror; passes along the tube, (at either end of which it is limited to a small aperture); it is then separated by the crystal, and finally viewed through a lens which magnifies the separation, and also reduces the irregular light to perfectly circular discs. Tubes of various lengths may be used as occasion requires.

ELECTROLYZING POWER OF A SIMPLE VOLTAIC CIRCLE.

MR. SOLLY has read to the British Association, a paper by Prof. Schoenbein, stating the effects of various experiments to establish the fact, that Voltaic effects may be produced without the solution of a metal, the usual source of voltaic action, but by nitric and various other acids.

CONTACT THEORY OF THE VOLTAIC PILE.

ON April 19, was read to the Electrical Society, a communication in favour of the Voltaic Pile, by M. Martens, of Brussels. The conclusions are briefly these :-The electrical condition of metals, or their electro-motive power, is altered by contact with certain liquids; their chemical reactions are thus changed; the condition of alteration only affects the parts immersed, and this, with the part emerging, constitutes a pair, the metal being electrically heterogeneous: different liquids modify to different degrees, and hence the same metal, with its ends in different liquids, constitutes a heterogeneous combination, and hence a voltaic pair: the current does not depend on chemical action the inversion of poles, attending the change to certain electrotypes, is due to the same property: metallic contact is the only direct cause of the galvanic current: chemical action cannot be, because electric tension is manifested before the circuit is closed: constant batteries owe their value to the same action of the liquid on the plates.

CONNECTION BETWEEN ELECTRICITY AND EVAPORATION.

MR. ROWELL, of Oxford, suspended two flat evaporating basins, of 8 inches diameter, by silk threads, over an oven in daily use, and placed in each of them eight ounces of water, then connecting one of them, by means of a thin copper wire, with the ground. After twentyfive hours, the quantity of water evaporated from the insulated cup amounted to 2 oz. 279 grs., whilst from the non-insulated vessel 3 oz. 144 grs., or 345 grs. more, were evaporated.-Philosophical Magazine, No. 128.

ELECTRICITY OF PLANTS AND VAPOUR.

ON February 15, was read to the Electrical Saciety, a paper 66 On the Electrical Relation between Plants and Vapour," by Mr. Pine. After adducing further experiments in illustration of the superiority of vegetable over metallic points in drawing off electricity, evidence is given of the operation of the same principle in nature; and it is shown that quiet fogs are electrical and lasting, because they do not move

from place to place, and pass among the conducting points of living vegetation; and that moving fogs are unelectrical and transient, because, in their transit from place to place, the vegetable points draw off their electricity, and at the same time effect their condensation.

ELECTRICAL GROWTH OF PLANTS.

MR. PINE, in a paper read to the Electrical Society, "On the tendency of Electricity to promote the Growth of Plants," dwells upon the positive state of the air, and the negative state of the soil. He brings many cases in proof that the luxuriance of vegetation is in proportion to these states. A drooping narcissus being removed into a room, the atmosphere of which was constantly surcharged with electricity from a machine often used for medical purposes, revived and attained the gigantic height of 36 inches. Mustard-seed, in a pot whose soil was negatively electrized, vegetated with greater vigour than seed in a positive soil, and far greater than seed in its natural condition.-Philosophical Magazine, No. 128.

NEW GALVANIC BATTERY.

M. J. A. VAN MELSEN, of Maestricht, has constructed this Battery, which is a great improvement upon the Wollaston: it is made by placing the plates as close as one-fifteenth of an inch by amalgamating the zinc, and by immersing the whole series in one undivided trough. The great increase of power obtained by these means was given in the lengths of wire fused by different arrangements.-Bullet. de l'Acad. Bruxelles; Proceedings of the Electrical Society.

POWERS OF A WATER BATTERY.

MR. H. M. NOAD, in a communication to the Electrical Society, states that two copper discs are connected with the terminals of a series of 500, and a pith ball insulated and suspended between the two, vibrates without cessation: it had been in motion a fortnight, with the exception of a few intervals, when it was removed to give place to other experiments.—Philosophical Magazine, No. 128.

FORM OF A VOLTAIC BATTERY.

ON November 15, was read to the Royal Society, a paper by Alexander R. Arrott, Esq.," On a form of the Voltaic Battery, and the mode of action of Chemical Affinity in the Voltaic Circle." Now that the Voltaic Battery is employed in several manufactures, and its use likely to extend soon to others, the saving of the zinc or positive metal, which is dissolved, is an object of interest. The construction also of batteries, in which an intense chemical force is obtained from other sources than metallic oxidation, suggests important theoretical inquiries. M. Becquerel obtained effects, as he supposed, from the combination of acid and alkali, which Mr. Faraday does not reject, although not fully included in his theory of voltaic action. Mr. Arrott finds, that they are only easily deoxidated acids, such as nitric and chromic acids, which thus act with alkalies; and that it is really their oxygen,

combining with the hydrogen of water, which produces the current, and not the combination of acid with alkali. The most efficient arrangement of this sort is ordinary nitric acid, a solution of sulphuret of potassium, separated by porous stoneware, with a plate of platinum in each liquid. A single pair will decompose water. The instrument exhibited, consisted of six pairs, each being a cylinder of one inch in diameter within, another of two inches, and both two inches in depth. The inner cylinder was porous, and contained nitric acid, of density 1.35; the outer cylinder contained solution of sulphuret of potassium, of density 1.14. Circular plates of platinum foil, which may be exceedingly thin, were placed in each liquid, and alternately connected. In short, the construction was precisely similar to Mr. Daniell's constant battery, except that both metals were platinum, and the fluids of course different. The battery described decomposed water to the extent of half a cubic inch of mixed gases per minute, for two or three hours. Deoxidation proceeds rapidly in the nitric acid, in which deutoxide of nitrogen appears; while a corresponding oxidation occurs in the sulphuret of potassium, or the oxygen of the former is carried, by a chain of voltaic decompositions, to the latter. Hence, the conditions of activity in such a battery are, attraction for oxygen in one liquid, (as in sulphuret of potassium,) and the power to supply oxygen readily by decomposition in the other liquid, (as in nitric acid). The more highly the two liquids possess these opposite properties, the more intense the action of the battery. The limit of this action was also shown to be the point at which the oxidating actions of the two liquids are equalized. Thus, when the liquids in the two cells, and in contact, are per-sulphate and proto-sulphate of iron, on connecting together the platinum plate from each, oxygen continues to proceed from the first to the last, till the proportion of per- and protosulphate of iron comes to be the same in both vessels.

ECONOMICAL VOLTAIC COMBINATION.

MR. F. W. DE MOLEYNS has explained to the British Association the following "Economical Voltaic Combination of extraordinary power." The author stated that, while the discoveries in electromagnetism gave promise of its ultimate application as a motive power far surpassing steam, it was matter of much importance to discover a mode of charging or giving attractive power to soft iron at a cost which should render it as a mechanical agent generally available. The voltaic arrangement now produced to the Society, the author believed, would be found to possess in a very great degree those advantages so much desired for the proper development of electro-magnetic energy. The combination consisted of acidulated solution of nitrate of ammonia, in contact with platina,-solution of muriate of ammonia and zinc ; the nitrate solution being separated from the muriate by a diaphragm of wood, biscuit-ware, or other porous substance not acted upon by the liquids. The acidulated solution is thus prepared: six ounces of nitrate of ammonia are dissolved in two fluid ounces of soft water, and this solution is then combined with an equal quantity, by measure,

of the pure sulphuric acid of commerce, adding the acid gradually; the vessel containing the mixtare being kept in a frigorific preparation, so as to prevent the heat evolved exceeding 100 degrees. The muriate of ammonia is dissolved in soft water to saturation. The zinc is not amalgamated, and the use of cast zinc is to be avoided. The platina is the thinnest foil that can be procured; but the author found that box-wood, cut to the thickness of veneer, and charred on each side superficially, might be substituted, and used with equal advantage. The author stated that, with a voltaic combination consisting of half a fluid ounce of the acidulated nitrate solution, one ounce of the saturated solution of muriate of ammonia, a strip of platina 3 inches by 2, surrounded by a piece of sheet zinc of equal surface, he had succeeded in supporting a weight of 2,000lb., with an electro-magnet of the horse-shoe form, measuring 16 inches from pole to pole, and three-fourths of an inch in diameter; and that the attractive force, before contact, was in proportion.

BICHROMATE OF POTASH FOR VOLTAIC PAIRS.

ON Jan. 18, the Secretary read to the Electric Society, a short account of the value of Bichromate of Potash in solution for exciting voltaic pairs. It had been employed, for the last six months, by Dr. Leeson, with much success. It admits of being used without a diaphragm; it produces a battery very constant in its action, and throws down a very good and abundant deposit of metal; for which purpose, indeed, it has been employed to some extent, in one of the many practical applications of electrotype to the useful arts.

USE OF IRON WIRE FOR SECONDARY ELECTRO-MAGNETIC COILS.

MR. J. E. ASHBY, B.A., of University College, London, informs us that fine Iron Wire covered with cotton may be substituted for copper in Secondary Coils, with an increase rather than diminution of effect, at less than one-sixth of the price, and with a great saving of space. Half a pound of this wire costs ls. 3d., and measures nearly 1400 feet.

With secondary coils so constructed, Mr. Ashby has been able, he states, to make the magnetic spark pass through nearly 1-100th of an inch between two wires, as in Mr. Crosse's experiments; and by means of a battery of about four square inches of negative plate, and a length of only 1100 feet in the secondary, to excite a current in the primary coil. Mr. Gassiot, Mr. Ashby observes, used for the same purpose 2100 feet of copper wire, and 20 large cells of Mr. Daniell's battery.-Philosophical Magazine, No. 139.

BLASTING BY GALVANISM.

MR. LYON, of Glasgow, the contractor for the new harbour at Dunbar, has successfully introduced the Galvanic Battery, to aid him in his extensive Blasting operations. Several explosions of considerable magnitude have taken place. The largest contained 60lbs. of powder, distributed in five bores of great depth. The bores were placed so as mutually to assist each other, and the conducting wires