tery principles long established by the researches of distinguished men at home and abroad: but I do claim the merit, whatever it may be, of the conclusions drawn from those principles as developed in the particular voltaic arrangement alluded to.

It only remains for me to add, that even supposing the principles of construction of the " sustaining battery were identical with Daniell's (which they are not), it would be extremely unfair to argue or assume that Mr. Daniell's researches furnished the clue to the plan of the other combination; for I unhesitatingly assert that for years before Daniell's constant battery was known, every, reader of the Annales de Chemie et de Physique, tome 41 (myself amongst the number), must have been fully aware of Becquerel's discovery in the year 1829, of the possibility of obtaining an equal current for a comparatively long period, by the employment of two fluids: one a solution of a salt of copper, the other diluted sulphuric acid, with a membrane (baudruche) interposed. In this combination the true principle of a sustaining battery was, beyond question, established; and although by reason of certain mechanical defects in the construction of Becquerel's batteries, as admitted by himself, the energy was not sustained, so long as it now is, by improved mechanical arrangements, I do insist that to Becquerel is justly and fairly due the honour of being the first promulgator and constructor of a constant voltaic combination of elements or materials similar to those subsequently employed by Daniell, and with the exception of the alkaline solution, similar also to those employed by me.

One word more, and I have done. Mr. Daniell sets forth in the letter alluded to, the "real principles of the constant battery;" and, inasmuch as he claims originality for those principles, and hints pretty broadly that such original principles have been made use of and applied by others in combinations claimed by them as equally original, it may be well to give, in his own words, his statement of the first of those principles, and answer him in the words of another, whose scientific reputation fully equals his own. Mr. Daniell says, in the first place, "I traced the origin of the decline and ultimate annihilation of the current in the common voltaic battery, not to the evolution of acid and alkaline matter at the opposite plates, and the consequent establishment of a counter current by their mutual reaction, but to the deposition upon the conducting plate of a substantial coating of pure metallic zinc; in consequence of this, zinc becomes opposed to zinc in the circuit, and all current is stopped." Dr. Roget, in his Treatise on Galvanism, published in 1832, page 14, after describing the effect produced by the contact of the metals in the circuit, proceeds as follows:-"The disengaged hydrogen will now appear upon the surface of the copper in place of the zinc,

• Our readers may expect a translation of Becquerel's paper in an early number.-Edit.

+ See Treatise of Galvanism in the "Scientific Treatises of the Society for Diffusion of Useful Knowledge."

without, however, apparently affecting the copper. In process of time, indeed, when a considerable proportion of sulphate of zinc has been dissolved in the fluid, the quantity of disengaged hydrogen is found to diminish, and a thin film, composed partly of metallic zinc, and partly of filaments of oxide of zinc, is deposited on the surface of the copper: as soon as this happens the galvanic action ceases.'

I need not here advert to Sir H. Davy's distinct statements on the same subject, for I believe they are too well known to need repetition: suffice it to say, that the deposition of metallic zinc upon the conducting surface, and other causes of the decline of voltaic energy were well understood for years before Professor Daniell produced the constant battery.

Mr. Daniell proceeds to say, that "his next principle was to prevent the deposition of active metal upon the conducting metal, by dividing the portion of the electrolyte in contact with the zinc, from that in contact with the copper, by a porous diaphragm, by which the solution of zinc is prevented from reaching the copper." Now, if deposition of zinc were the sole or chief cause of the decline of voltaic energy, one fluid, so divided, would have answered every purpose; but this was not so, therefore it appeared requisite to introduce the salt of copper. But it so happens, that when a cupreous salt is employed, though there should be no diaphragm, there is no deposition of zinc on the conducting metal; and I have found, and M. De la Rue and others have proved, that the energy of the battery so charged, may be sustained for a long period without any diaphragm; therefore, upon the ground of preventing deposition of zinc, Mr. Daniell's protection of the negative metal was unnecessary, and therefore that part of his principle cannot be sustained. For the above reasons I did not adopt a diaphragm "for the purpose of preventing a deposit of zinc upon copper," but for the directly opposite purpose of preventing a deposition of copper upon zinc.

Regreting that I have been compelled to thus defend myself from most unwarrantable insinuations, as well as support my just title to whatever merit may attach to a form of voltaic combination which, for sustained as well as powerful effects, is now pretty generally appreciated; and assuring Professor Daniell that I have no wish to deprive him of any credit to which he may be fairly entitled; or to insinuate that he read, or had read to him, or heard of M. Becquerel's researches, as published in the Annales de Chemie, tome 41, or subsequently, either in the Annales, or any other scientific work, foreign or domestic-I feel that I have stated quite sufficient to prove that I am no imitator of the Professor, and shall, therefore, not be again induced to notice such uncalled-for attacks, no matter from what quarter they may emanate.

Bruxelles, April 9, 1842.

I am, dear Sir, your's faithfully,
F. W. MULLINS.*

• A full description of Mr. Mullins's "sustaining battery" may be seen in vol. 1 of these Annals.-EDIT.

Memoir on the General Principle of Natural Philosophy. By M. G. LAME, Professor at the Polytechnic School.*

THE discovery of ether is due to the physical theory of light; the idea of luminous undulations, defended by Euler and Young, has had a definite triumph by the discoveries of Arago and of Fresnel; since the fruitful theories of the latter, the more recent works of MM. Hamilton and Lloyd, Brewster, Babinet, Seebeck, and the mathematical researches of MM. Cauchy, MacCullagh, and Neumann, it is no longer possible to doubt the existence of ether. The physical theory of electricity, excited by the discovery of Ersted and the works of Ampere, all conjoin at the present day to make all the electrical phenomena depend on the mutual actions of ether and the ponderable matter; and it is evident that to this preconceived idea are due the greater parts of the discoveries of MM. Becquerel, De la Rive, Faraday, and Savary. In fine, the physical theory of heat, since the works of MM. Melloni and Forbes, is in vain defended against the idea of vibrations.

In resuming the subject, the general principle, towards which the three partial theories of natural philosophy at the present day converge, attributes to ether, to its own repulsions, and to the actions which the ponderable matter exercises on it, all the phenomena which depend on these theories. The propagation of the vibrations of the etherial fluid gives light, and all the radiations. The increase or diminution of the masses of ether, which form the atmospheres of ponderable atoms produces electricity and chemical phenomena. In fact the vibratory movement of these atmospheres gives heat.

This principle contains in itself all the hypotheses elaborated by the philosophers who occupy themselves on the different departments of philosophy; it embraces and explains sufficiently the phenomena of all classes. This generality does not show, without doubt, its real existence, but it gives to it, at least, as much of certainty as to the original ideas of modern discoveries, since these ideas are found to be comprised in the complete expression of the principle which it contains. The consequences deduced from this principle present themselves with a probability then sufficient to attract the attention of philosophers.

One of these consequences is the existence of a pressure exercised by the ether on itself, on all other bodies, and in the interior of all the millions of other ponderables. The non-manifestation of this pressure results from the fact that there is no body in existence entirely deprived of ether; and that because all the particles of the fluid communicate freely among them, by the layers which separate the ponderable atoms, whose complete contact nowhere exists. This pressure ought to surpass in greatness the cohesion of all the trans

Comptes Rendus, Jan. 3, 1842.

parent solids, for it is that which maintains them: as the atmospheric pressure maintains the liquids which evaporate in a vacuum. But again, if we take a glimpse at any kind of barometer which can give us the exact amount of this pressure, there exists the means of proving its variation; such is, amongst others, the measure of the co-efficient of the dilatation of the gases. If the pressure of the ether is greater at the present day than at the epoch when M. Gay Lussac measured it for the first time, in an exact manner the dilatation of the gases, the two fixed points of the thermometer, ought to approach each other; which explains in a very simple manner the non-agreement of the co-efficient measure at two epochs. In fact, after the actual memoir :

1st. The tension of the vapour of water, measured at a determined temperature, is only the excess of its total elastic force on the pressure of the ether in vacuo; and if the pressure augments, the vapour ought in reality to be raised in temperature, inasmuch as its measured tension remains constant. That is to say, that the fixed point for the ebullition of water, under a barometric pressure of Om.76, ought to be higher.

2nd. The fusion of a solid takes places when the resultant of the interior repulsive forces surpasses a little the pressure of the ether; that is to say, that the degree of the fusion of a solid, under the pressure of the ether, is analogous to that of the ebullition of a liquid, under the atmospheric pressure. Then, if the pressure of the ether is augmented, the temperature of melting ice ought to be raised.

The ascending variation of the fixed point of melting ice ought to be much greater than the variation in the same direction of the fixed point of ebullition. From some experiments of verification (in which I have been assisted by M. Cobart), I have proved that the tension of the vapour of water, at the temperature of melting ice, is still at the present day 5"", as M. Gay Lussac found it at an epoch but little removed from that in which he measured the dilatation of the gases. We may, then, say at the present day, as then, that the temperature of melting ice is that where the tension of the water is 5mm. This concordance proves that the resultant of the repulsive forces in the ice, and the elastic force of the vapour of water, at the temperature in which ice melts, preserve a small constant difference, whatever be the variation which this temperature may undergo through a change in the pressure of the ether.

However, it is sufficient to consult the table of the tensions of the vapour of water, in order to see that if these tensions represent the excesses on the pressure of the ether, an augmentation in this latter pressure ought to raise the temperature at which the measured tension is 5; that is to say, the zero of the thermometer, of a quantity of from seventy to eighty times greater than the correspondent variation of the point of ebullition, or of the temperature at which the measured tension of the vapour of water is of 760mm. Thus the two fixed points of the thermometer ought to approach each other.

It is to be presumed, then, that the non-accordance of the number found, during twenty-five years, by M. Gay Lussac, to express the co-efficient of the dilatation of gases with that found at a later period by M. Rudburg, and verified by M. Regnault, results entirely from variations of this nature. The difference of the two results explain themselves, by admitting that the pressure of ether has undergone on the earth, in a quarter of a century, an augmentation equivalent to a pressure of eight or nine-tenths of a millimeter in height of the mercury a small increase, but which will suffice, however, to bring nearer to each other the two fixed points of the thermometer by 2 degrees, taken on the old divisions; for by dividing the total dilatation of the air between the two fixed points, obtained by M. Rudberg by 97.75, and not by 100, we re-obtain the number given by M. Gay Lussac.

Professor STEINHEIL on a simple Method of Showing the Existence of Induced Counter-Currents by Direct Experiment. From the Gelehrte Anzeigen, Munich, Dec. 1, 1837. Translated by W. LETTSOM, Esq.

BETWEEN the poles of a compound horse-shoe steel magnet let there be adapted a rotating anchor of soft iron, surrounded with covered wire. The ends of this wire dip down into mercury cups separated by a partition, the cups themselves being brought into connection with the terminal wires of a battery. Between one of the above cups and the battery a multiplier is to be inserted.

As soon as the battery is set in action, the anchor between the poles begins to rotate; and let us suppose the needle of the multiplier to be deflected at the same time to the right. Now break off the connection with the battery, and spin round the anchor by the application of some mechanical force in the same direction in which it was previously impelled by the battery: the needle of the multiplier will be deflected in the opposite direction; that is to say, to the left, and the amount of this deflection increases with the rapidity of the motion imparted to the anchor.

By the rotation of the anchor, caused by the battery, there are, therefore, currents of opposite signs called forth, and in which the counter-current is stronger the more rapid the motion is, or the greater the strength of the magnet is, and from which there must naturally result a proportionate, and not an accelerated velocity; and as a further proof of this, it may be added, that the velocity of the rotating apparatus is increased the very instant that the magnetic power is reduced by the application of an anchor-that is to say, while we weaken the magnet, we reduce the power of the induced

counter-current.

This experiment appears so convincing, and so irreconcilable with Moser's views on electro-magnetic machines—namely, that the