to which light must transform itself to be able to unite with their bases. The nature of this power is farther confirmed by that which is requisite to disengage permanent aeriform combinations. rent, or by a In the compositions and decompositions of substances by assists in the one another, it acts sometimes by concurrent at others by composition or decomposition disposing affinity. In the first case it unites with one of the of substances principles of the substance, which principle must always be by a concura base of a permanent gas; and in the second it merely fa- di posing affvours the action of a second principle by acting as heat. nity: Thus it occasions the oxidation of metals by water, by converting the hidrogen into gas, &c.; and calls into action the affinities of all substances in the same manner as caloric, by diminishing their attraction of cohesion, or dissolving them. direct co binations; by carrying along in ir ele ments with dif ferent veloci It is as caloric too, that it effects direct combinations, such as heat effects as those of the bases of water, &c. It decomposes, and that particularly in the current of the decomposes pile, certain insulated substances, on the principles of which substances it exerts no attraction but that of conveying with different velocities. This action, I confess, is singular, and supposes in the fluid a great attraction of adhesion to the principles of these substances, as it can make them follow the rapidity of its translatory movement. The decompositions of salts with indecomposable acids and bases particularly take place in this way. I have remarked, that this action is scarcely at all exerted by the pile, when the communication is established by means of thick wires, or other substances with an extensive surface. ties: combinations by concentra To effect combinations that require a red heat, as most effects some combinations, &c., the fluid should be made to through pass a stratum of air, in order that it may concentrate itself suf- ting itself into ficiently to force this passage through a medium, which 1e- the state of light and heat: fuses it as a nonconductor, and thus establish itself in the state of light and heat. Thus it is in quality of these two modifications of caloric, that it produces inflammations, &c. The presence of light appears to be necessary in these operations, to impart the luminous constitution to the electriform caloric, which converts the oxigen into gas. It appears, that, every time the electric fluid no longer and in part asfinds occasion to exercise its attraction of adhesion and ex- sommes the state when its ten dency to expand is so re pansion on bodies, as in gliding along a nonconductor, in traversing a nonconducting medium, in a vacuum, &c., it strained by a assumes in part the state of light. This attraction of adnonconducting hesion is always the result of the tendency of the fluid tỏ expand, and of the restraining action of the air. medium, as to exercise the attraction of adhesion. To return to the theory of electricity, beside that SymObjections to mer's, namely the hypothesis of two fluids, or rather of the hypothesis three, the resinous, vitreous, and both combined, is more of two fluids, complicated; and that we perceive no difference between the two fluids in respect to their action, for the operator can only judge by the comparison and opposition of these fluids, whether he have excited the one or the other, a circumstance which has nothing analogous to it in natural philosophy; which is shown this hypothesis is fundamentally overturned by the fact, that to be funda mentally wrong. Franklin's theory. Always acts by attraction, glass and resin excite both the electricities indifferently, accordingly as they are rubbed with substances more or less conducting than themselves. The Franklinian theory on the contrary is simple, adapted to the nature of things, and agrees with the received doctrine of the exercise of inaterial powers; its attractions and repulsions are effects of the same cause, and the natural result of an elastic fluid, eager for an equilibrium, the opposite states of which, in order to find this equilibrium, rush from the place where it is plus toward that where it is minus, carrying with it the substances on which they are excited, if these substances be light, and freely suspended, or movable. It is never repulsion therefore, but always attraction, that causes the motion of these substances, which in the ball electronieter separate by the communication of positive electricity, for the purpose of depositing the excess of their fluid on the sides of the glass, in which this excess has excited a state of defect; and by the communication of negative electricity, to repair their defect of fluid from the same sides of the glass, in the substance of which this defect has excited a state of excess. The same thing takes place in the air: besides, the separation in both cases is necessary for the formation of the opposite atmosphere, without which no electrical charge can be established or retained, and no discharge take place. In this appears to the other cases of alternate attraction and repulsion, as in abernate with that of an insulated ball immersed in the atmosphere of an repulsion. even where electrified electrified substance, this ball only acts the part of a messenger, or serves as an instrument to reestablish an equilibrium between the opposite states. Hence it was erroneous to oppose to the theory of one sole fluid, with the affectation of so much confidence, the phenomena of repulsion between two substances negatively electrified, and the direction of a needle to the same point, whether moved by a current flowing to it, or a current escaping from it. In one case it moves to get rid of the fluid received, in the other to regain that which has been taken away. densed round No intelligent partisan of the theory of a single fluid ever Air never consaid, that the air condenses round a substance negatively a substance electrified, or electrified by subtraction. electrificd minus. crucis. In the experiment proposed by Girault to decide between Girault's exthe two theories, an experiment that has been a thousand perimentum times made, the fluid is not transferred from one coating to the other, but diffuses itself in the void space, which no longer offers the resistance, on which its condensation and its adhesion to substances depend: yet as in this experiment the vacuum cannot form at once, the electric fluid separates in succession as the air rarefes, and prevents us from observing whether it flow from the exterior or interior surface of the bottle. For this experiment it is not necessary, to charge the bottle at a machine with a plate of resin: for to charge it negatively within, it is sufficient to present its outer coating to the conductor, while its interior coating communicates with the ground, or to charge it in the usual way, presenting its hook to the cushions of a machine, the conductor of which is not insulated. In electrical experiments made in vacuo, the fluid that ceases to be applied is transformed into light, traverses the receiver, and is dissipated in the air. I have written you insensibly a long letter, yet what I have said has not been the more interesting on this account. My head and my papers are filled with memorandums of facts and ideas, which my occupations do not allow me to set in order, and which render me diffuse when I have occasion to speak of them. Fusion of a stone with al kali alters the ples. V. Description of the Process I have employed to ascertain the existence of Alumine in Meteoric Stones, by B. G. Sage, Member of the French Institute, Founder and Director of the First School of Mines*. MARGRAFF and Bayen procceded to the analysis of stones by vitriolization, because they had found, that fusion nature of some through the medium of alkalis altered the nature of some of its princiearth. This appeared to me unquestionable, since chemists the most justly celebrated, as Klaproth, Fourcroy, Vauquelin, &c., who have given analyses of the meteoric stones, named aerolites by Mercati, have not mentioned the alumine, which I can affirm exists in them: for, having vitriolized some of the meteoric stones of Aigle and Salles, near Villefranche in the Lyonese, I obtained alum from both, but in unequal proportions, since the aerolite of Aigle yielded me near a fourth, while that of Salles did not afford above an eighth. Alumine in meteoric stones. That of Salles leable iron. I powdered and sifted through a silk searce some of the contained mal- meteoric stone of Salles, an eighth part of which was irreducible to powder, because it contained portions of malleable iron, attractable by the magnet. This, being fused with glass of borax, produced ductile iron, that had the brilliancy of the purest steel when passed through the flatting mill; while the malleable iron obtained from the aerolite does not assume an equally brilliancy after being laminated. A portion of this iron had coloured the glass of borax black, and rendered it attractable by the magnet. Treated with To vitriolize the magnesia and alumine, which make part sulphuric acid. of meteoric stones, I introduced into a retort eighteen nominal cwt. of the aerolite of Salles, powdered and sifted; poured in an equal quantity of concentrated vitriolic acid; and proceeded to distil to dryness in a reverberatory furnace. Sulphurous acid was at first evolved, accompanied with yellow sulphur, which was found in the proportion of a * Journal de Physique, vol. Ixvi, p. 460. thirtieth thirtieth in the meteoric stone. At the bottom of the retort was left a grayish mass, which, after having been diluted in three parts of water, produced a sensible heat. This solution, when filtered, was of a fine green colour, Solution filterowing to the nickel and iron. When evaporated, it pro- ed and evapoduced by refrigeration tetraedral prismatic crystals of a light green. rated. alumine crys The crystallization being confused, I dissolved the salt, Sulphates of and obtained crystals of two distinct forms. Those of vi- magnesia and triol of magnesia were in tetraedral prisms, intermingled tallizedwith crystals of alum, exhibiting octaedra bisected diagonally. Both these salts had a green tinge. The small quantity of alum produced by this first vitrio- Residuum lization showed me, that only a part of the alumine was acted treated afresh with sulphuric on. I therefore distilled the dried residuum, which was di- acid. minished five nominal cwt. with eighteen nominal cwt. of vitriolic acid. The residuum, after being lixiviated, afforded me a solution less tinged with green; which, being evaporated, yielded me more alum than the former. The residuum of this lixiviation being dried and weighed, I found there were two nominal cwt. of alumine and magnesia vi- More alumine triolized in this operation. and magnesia. In order to disengage the last portions of alumine and Treated a magnesia, that remained still interposed among the silex, or pulverized quartz, I distilled the residuum a third time. with twelve nominal cwt. of concentrated vitriolic acid. third time with sulphuric acid. More alumine After what remained in the retort had been lixiviated, filtered, and dried, I found that the sulphuric acid had vitriol- and magnesia. ized two more nominal cwt. of alumine and magnesia. By distilling the residuum a fourth time with vitriolic acid, I satisfied myself, that it contained no more alumine or magnesia. Nothing remained in the retort but very white silex, weighing nine nominal cwt. When I analysed the meteoric stone of Aigle, I added to- Meteoric stone gether the solutions of the three vitriolizations, which, on of Aigle. being evaporated, produced me at first alum, and afterward vitriol of magnesia. But in the analysis of the aerolite of Salles, I evaporated the solutions of the three vitriolizations separately and hence I learned, that the sulphuric acid vitriolized the magnesia first; since the first lixivium yielded but |