¡received. We may likewise heat wires by the electricity of contact. t. To produce this effect, we must employ large metallic in to collect a great quantity of electricity relative intensity. Co order to 93 Vil. Such is the induction, from which Prof. Ersted concludes that it is a general law that bodies become HOT whenever they are forced to conduct a greater quantity of electricity than they can freely transmit. In such cases there is always a considerable accumu Iation of the opposite electricities before they unite. It is this union of the two electricities which produces heat. Professór Ersted does not explain himself with regard to the nature of heat. He does not inform us whether it be a substance é formed by the union of the two electricities, as was the opinion of Winterl. Indeed from his mode of expressing himself, he seems rather to be of opinion that the two electricities are not substances, but forces; and that heat is a force composed of the two opposite electrical forces united together. If this be the nature of his theory of heat, I confess that I am unable to form any accurate conception respecting it. I can conceive opposite forces rendering each other insensible by their mutual action; but I cannot conceive them to unite together, and form a new force of a different nature. I can form a conception of what Winterl means when he says, that heat is a substance composed by the union of the two opposite electricities, provided these electricities be substances; but if they are merely opposite forces, the affirmation that heat is produced by their union seems to me at least to be merely words destitute of ideas attached to them. As I am unable to perceive the accuracy of the reasoning in the following paragraph, in which Prof. Ersted deduces some of the most striking particulars respecting heat as consequences of his theory, I shall present the reader with a literal translation of the passage. "This action (the union of the two electricities) ought, therefore, to disappear in a point of space just when it begins to act in the succeeding point. Accordingly it leaves no trace as long as it meets with no obstacle; but when it meets with resistance, the case is quite different. The force which ought to accumulate in the place where the obstacle occurs, not being at liberty to put itself in equilibrium with an opposite force in the prolongation of the line, turns its action towards another point where there is less resistance, in order to continue to act in the same Tane The manner. This is what happens in the reflection of heat. new direction will be determined by the direction which it had before, and by that of the resistance; and may be determined by the fundamental principles of mechanics, which point out the law known to all the world that the angle of reflection is equal to the angle of incidence. It is easy to see that all that we have deduced here from our principles applies perfectly to radiant heat. We shall continue a little further the examination of this calorific 3 Ը action molt is obvious that heat ought to be better reflected by the surfaces which have a metallic lustre than by those which want that lustre because this lustre indicates that the surface has little inequality, especially in the smallest parts. But we know likewise that the forces of which we are treating are transmitted more easily by means of points elevated above å surface than by those that form a level surface. Hence we see that bodies with a brilliant surface ought not merely to reflect Tyto more perfectly the external heat which endeavours to penetrate into them, but likewise the internal heat which endeavours to escape, as has been proved by the beautiful experiments of Leslie and Rumford. According to our principles, those bodies which are the least capable of conducting a great quantity of electric forces are the most proper to transmit this calorific action; for they are most proper for its production, and its propagation is merely a continued production The small number of experiments to which we can at present apply this principle confirm it; especially the great facility which we find in all the gases for this sort of transmission. It would be requisite to ascertain whether the oils do not possess the same property in a higher degree than all other liquids. 3 The opposite forces in bodies are disturbed by frictionlfone of these forces be permitted to make its escape by opening a communication with the earth, we have the phenomena of elec tricity; but when this separation does not take place,qnothing takes place but but an internal change in the equilibrium and in uence, the different phenomena of heat. Prof. Ersted then shows at considerable length that the evolution of heat by friction is inconsistent with the common theory which supposes Calorific matter; but that it is perfectly consistent with his! own theory that heat is the consequence of the union of the two electricities in particular circumstances. vd as The quantity of the opposite forces which exists in each body appears then to be very great. The chemical properties of the body depend upon the preponderating force but the preponderating quantity must, in all cases, be very small, when compared with that of the forces which are in equilibrio. The dilatation of goodies is not owing to the preponderating force, but to the expansive property of those forces which are in equilibrium, and which produce a dilatation which is greater or less according to the intimacy of their combinations; for a body occupies the less volume the more intimately its forces are united, and is the more dilated the less intimately they are united. Hence a hot body in which the equilibrium of the forces is more disturbed ought to be more dilated than a cold body in which the equilibrium is more intimate. 201102 HTIW author in The remainder of this the chapter is taken up by our showing that all the facts respecting heat with which we are acquainted follow naturally as consequences from his theory. These facts are chiefly the following That all Bodies contam + heat; 2. That heat changes the state ofo bodies, donverting solids into liquids, and liquids into elastic fluids 3.9 That hedi favours chemical combinations and decompositions 64t That heat as disengaged in every case of chemical pcombinationg 5. That bodies have different capacities for heat ;96. That when 16. solids are converted into liquids or liquids into vapours, a certain quantity of heat always disappears. These phenomenas are accounted for in a very simple and satisfactory manner. Indeed the only thing that our author's theory of heat wants is to be expressed in a more precise and definite manner. Sodda ocmi to atmomitoggs Liturad (Tot be continued.)d zed as 993069 asibodoseal Korf bar sil29J To visurup tap 6 gal ofiles aut timnast eti bus oitoubory a ARTICLE VII. Home 9dT Proceedings of Philosophical Societies. aidt vlque traz2314 36 199 baftsw doldw vildLINNEAN SOCIETY. March 2A paper, by the Rev. W. Kirby, was read, on the characters of the Otocerus and Fulgorella, two new genera of Hemipterous insects belonging to the family of Cicadiada, with a description of several species. s Also an account, by Mr. J. Drummond, of some experiments made in the Cork Botanic Garden, by sowing the powder found in the ripe capsules of Funaria hygrometrica. 18 tud 9o8la sedet ni March 16, Mr. Lindley's monograph of the genus rosa was dontinued.or 269d to rebienoo awoda nedt April 6--A paper, by R. Brown, Esq. was read, on Lyellia, anew genus of mosses, with some remarks on Leptostomum and Buxbaumia.izianos víte shoq ai OvAt this meeting there was also begun a memoir on the birds of Greenland, by Capt. E. Sabinę. ViAdpaper was likewise read, entitled "Remarks on the Changes of Plumage of Birds," by the Rev. W. Whitear. -April 20.44Capt. E. Sabine's account of the birds of Greenland was continued. 207 ,297£5 Ha ft Jeum yjuneup gra At this meeting was also read, an account, with drawings, of vegetable specimens found in the coal-pits in the neighbourhood of Camerton, by the Rev. Mr. Skinner. To q of gribrosos ar to 1979rg ai do de noittelib a souborq dolde CONNECTED WITH SCIENCE. ni rodams 1:1. Specific Heat of Fluids and 969 doid. An Heat of Fluids and Solids, tedt gniweda M. Dulong is stated to have been led to conclude from his s recent experiments on this difficult subject that the specific heatTM. of all the simple gases is the same, and that the specific heat of simple solids is proportional to their capacity for oxygen. These laws, if well founded, may be justly classed among the most important developed by modern chemistry. II. Euclase. Berzelius has lately subjected this beautiful and scarce mineral to a more accurate analysis than that of Vauquelin, who sustained a loss of 21 per cent. The result of Berzelius's analysis is as follows: From this analysis, Berzelius concludes that it is a compound of one atom of silicate of glucina and two atoms of silicate of alumina. Vauquelin's analysis gave the following constituents of this mineral: III. Iron Ore of the Isle of Elba. Crichtonite possesses a peculiar metallic lustre, which belongs also to the iron ore from the island of Elba. This circumstance led Berzelius to suspect the existence of titanium in this latter ore. On making the experiment, he found his conjecture verified. The presence of titanium in this ore indeed may be discovered by the blow-pipe. Dissolve before the blow-pipe a little of the Elba ore in the double phosphate of ammonia and soda, and then reduce it completely by exposing it to the interior flame of the blow-pipe. The colour of the iron disappears almost entirely during the cooling, and at the instant that the globule becomes solid there appears a reddish orange colour, which is owing to the presence of titanium or wolfram. Berzelius ascertained that in Elba iron ore it was titanium which was present. IV. Yellow Oxide of Uranium of Autan. From an analysis of this ore lately made by Berzelius, it follows that it is a uranate of lime containing a great deal of water of crystallization. That of Cornwall is the same combination coloured by arseniate of copper. V, White Pyrites, or Radiated Pyrites. It is well known to mineralogists that the crystalline forms of this variety of pyrites are quite different from those of common pyrites, and cannot be mathematically deduced from them. On that account, Hauy has constituted it into a peculiar species, under the name of white pyrites. Werner distinguished it under the name of kammkies. Berzelius has lately subjected it to a careful analysis, at the request of M. Hauy, to determine whether any difference existed in its composition, as had been inferred from the difference in its crystalline characters. But he has been unable to discover any distinction whatever between white pyrites and common pyrites. He proposes to repeat his experiments on other specimens. Does this mineral constitute an exception to the science of crystallization as seems to be the case with arragonite? VI. Phosphate of Manganese of Limoges. "This mineral was discovered some years ago by Alluan, and sent to Vauquelin as an ore of tin. That celebrated chemist it to subjected analysis, and ascertained its composition. It has been lately subjected to a new analysis by Berzelius, who has found it a compound of one atom subprotophosphate of iron and one atom of subprotophosphate of manganese. The constituents extracted from it were as follows: Mineralogists are well acquainted with a variety of quartz which Werner, from its texture, denominated fibrous quartz. Mr. Zellner, of Pless, lately analyzed a specimen of this variety of quartz, from Hartmannsdorf. He found its constituents as follows: |