chemistry of the arts, F. Accum, M. R. I. A.-Natural philosophy and Astronomony, Mr. Hardie. electrochem Mr. Singer's lectures on electrical and electro-chemical Lectures off science will recommence early in the ensuing season, at the electrical and Scientific Institution, 3, Princes Street, Cavendish Square. cal science. In these lectures a complete exposition of the subject will be given, and the illustration will be assisted by some new and interesting experiments. A prospectus of the plan of instruction may be had at the Institution, or of Mr. Cuthbertson, 54, Poland Street. Mr. Barlow, of the Royal Military Academy, has ready Investigation for the press, an Elementary Investigation of the Powers of the powers and properties and Properties of Numbers, with their application to the of numbers. indeterminate and diophantine analysis, to which will be subjoined a synopsis of all the most curious problems of this kind, selected from the best ancient and modern authors. To Correspondents. The paper of Messrs. Kerby and Merrick in our next. NATURAL PHILOSOPHY, CHEMISTRY, AND THE ARTS. DECEMBER, 1810. ARTICLE I. On the Electric Column. By J, A. De Luc, Esq. F. R. Ś, PART III. Concerning some Meteorological Phenomena, to the better knowledge of which it may lead as an Aerial Electroscope. WHEN, in our researches, we have in view some great Necessity of on in examin and determined object, we are not only more assiduous in circumspecti our endeavours to approach it, but more attentive not to be ing phenome misled in the road, and less disposed to be satisfied with na. mere surmises, while we perceive that some real discovery may be obtained by more circumspection, I shall therefore explain first, why every new electric phenomenon, which we encounter in the course of our experiments, must be attentively pursued and analysed in itself, and not connected with gratuitous hypotheses; for fear of losing a thread, which might lead us in the labyrinth of the physical causes acting on our globe, among which the electric fluid holds a high rank; as will appear by the following great object concerning this fluid, on which natural philosophers have not yet sufficiently fixed their attention, though it is explained in my former works. VOL. XXVII. No. 124-DEC. 1810. R It Lightning. The electric fiuid not accuinulated in a It is commonly supposed, that the electric fluid, which, under the form of lightning, darts from certain clouds, existed previously in them, ready to be discharged, at a proper distance, on bodies which possess less of this fluid, either other clouds or the ground. On this idea, not improbable at first sight, Dr. Franklin founded his invention of Conductors. pointed conductors elevated above houses, in hopes to preserve the latter from being struck by thunder bolts. With the above supposition, this method of security was very ingenious; for, if the electric fluid were actually accumulated in a cloud, ready to be discharged on the first part of the ground sufficiently elevated, a pointed conductor might discharge that cloud without a spark, as it does the prime conductor of an electric machine. But those who have frequently travelled on high mountains know certainly, that there is no analogy between a thunder cloud, and an insuthunder cloud. lated body on which electric fluid has been accumulated. A cloud is a mere thick fog, and thus such a completely conducting medium, that the most powerful electric machine worked in it could not, for an instant, accumulate the electric fluid on its prime conductor; it would be constantly diffused through that moist air, and lost in the surrounding bodies. This cannot be doubted; but it is supposed, that clouds, being surrounded by pure air, and thus insulated, can retain the electric fluid accumulated in them by whatever cause. In this consists the illusion, dissipated by what is observed on mountains. I have frequently been in valleys of the Alps, and of lower mountains, beset with thunder clouds leaning on both sides against wet grounds, and thus in so complete a conducting connexion with the mountains themselves, that it was impossible any accumulation of electric fluid could remain in the former; beside which, no cause of such an accumulation has ever been explained: however flashes of lightning were emitted from these clouds, with greater or smaller intervals, followed by the astonishing phenomenon of the rolling of thunder; and to suppose this to be the repetition of one sound, by echoes from cloud to cloud, is a fiction similar to that of poets of painters, who represent the gods as sitting on these fogs. Lightning cess. Lightning and thunder, when considered in their true Thunder and nature, and with all their associated circumstances, though lightning they are the most striking, have remained till now the most obscure of the atmospheric phenomena; and as at the same time their production is evidently connected with all the causes acting in the atmosphere, that great laboratory of nature on our globe, beginning from the very formation of clouds, this obscurity is spread over all the terrestrial pheno mena. It is certain, by what I have above explained, that an instant before a flash of lightning strikes our eyes, no accumulation of electric fluid could have existed in clouds leaning against wet grounds: the sudden manifestation of this enormous quantity of electric fluid, not existing before the conse as such, must therefore be the consequence of some chemical quence of some chemical prooperation, depending on some new cause, which either disengages it from some combination, or generates it by some composition; and being thus instantly set free, it rushes in a torrent, before it can be diffused in the cloud and through this in the ground. Beside this immediate consequence of the certain fact, that the quantity of electric Auid thus emitted did not, the instant before, exist as disengaged in the cloud, various other phenomena, attending this effect, prove the existence of some great successive chemical processes, manifested principally by the successive detonations forming what is called the rolling of thunder: these are undoubtedly produced by concomitant decomposis tions and recompositions of still unknown atmospheric fluids, some producing the decomposition of the air itself, others proceeding from this first operation, as shall be explained hereafter. atmospheric phenomena, This is one of the greatest objects, that could be offered to Necessity of the attention of natural philosophers: for it must strike investigating them, that no system on the nature of air and water can have any solidity, if it happens to be in opposition to these grand effects produced, under our inspection, in the great laboratory of nature: and though our observation has not yet extended to all the atmospheric phenomena necessary to be embraced for the discovery of their specific causes, yet it is sufficiently advanced to indicate, according to general Atmospheric known laws, these decompositions and recompositions of air not a mix. R 2 atmospheric ture, |