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for three additional years. For this new period the past had been an excellent preparation; all improvements that experience could suggest would be adopted; the correction for the temperature of the magnets, which is found to be the most important of all, will have been determined. But the past had not been merely a season of preparation, it had afforded demonstrations of the ubiquity of those singular disturbances called magnetic storms, which could not otherwise have been obtained, and data for the revision of the Gaus sian theory. As to magnetic surveys, in South Africa, Lieut. Clarke, R.A., had joined the observatory at the Cape, as assistant to Capt. Wilmot; and it was proposed that the survey should comprehend, in addition to the colony, as extended a portion of the earth's surface, from the observatory, as circumstances would permit. The Admiralty had instructed the Admiral on the station to permit the sea portion of the survey to be carried into execution, so far as it was not prejudicial to the service, in her Majesty's vessels, and these, surveys would include the coast on each side the Cape, and then we should be better able to judge of the expediency of completing the survey by an expedition into the interior. In North America, Lieutenant Lefroy, R.A., had been appointed to the principal observatory at Toronto; and was now in England preparing instruments. The Hudson's Bay Company had liberally undertaken to furnish conveyances in the years 1843-4 and 1845, to extend the surveys to the Pacific Ocean; and they also made an offer of passages on board their annual ships to England, and this would enable them to include in this magnetic survey Hudson's Bay and Straits. In the United States, Professor Bache (of Philadelphia), during the last summer, had completed the survey of Pennsylvania, commenced in the previous year, including three series of observations: the declination, inclination and intensity. Professor Loomis had extended his observations of inclination over a great part of Ohio, Indiani, Illinois, and Missouri. These, and numerous other observations and surveys in the States, would connect the northern British survey with the determinations of Capt. Barnett, of the Thunder, in the gulf of Mexico. As to observations at sea, by Mr. Fox's instrument, the inclination and dip of the magnetic intensity might be measured with all the precision requisite for every use to which observations at sea could be turned, for the purpose of tracing out the isodynamic and other magnetic curves in portions of the globe covered by water. To extend and facilitate the use of this valuable instrument, the set of instructions drawn up by Col. Sabine had been printed by order of the Admiralty, as a general circular, with some statements of the mode of using it practised on board the Erebus and Terror; and the hope was expressed that this method would be followed, not only in exploratory voyages, but by ships pursuing ordinary tracks, so as to furnish data for complete magnetic sea-charts. For these important observations, as well as the declination, it was necessary to eliminate the influence of the ship's iron: an evil increasing from the greater quantity of iron now

used. After mentioning the observations of Capt. Belcher, of the Sulphur, on more than twenty islands in the Pacific seas, which had arrived in England, and would be published, and the important results deduced from M. Erman's journey in Siberia, the report noticed the subject of magnetic disturbances, respecting which Gauss remarked, that one of the results of this great British enterprise was that the existence and extension of these disturbances over the whole of the globe had been ascertained. As a physical fact deeply connected with the general causes of terrestrial magnetism, this was indeed a result of the first magnitude; and considering all the circumstances, how it was modified by distance and locality, was eminently calculated to lead to theoretical truths. It distinguished what was local from what was general, and traced individual shocks from observatory to observatory, and station to station, till they were so far enfeebled as to be confounded and masked by the growing influence of other shocks nearer the principal point of observation. The report recommended smaller bars than those now in use, as more easily affected by sudden shocks. It was now considered advisable to collect from all sources to which we had access, accounts of the remarkable disturbances, beginning with 1840 and 1841, arranging them in chronological order, and publishing them in volumes by themselves, and the first volume would be published in the course of this summer. The great disturbance of the 25th of September, 1841, which was observed at Greenwich, and was immediately made the subject of a circular from the Astronomer Royal to his brother observers, was also observed at Toronto, St. Helena, the Cape of Good Hope, and Trevandrum in Travancore. All these arrived in time to be inserted in the volume for 1841; and surely it must be regarded as a remarkable fact, that this casual phenomenon was seized upon by our observers in Europe, Asia, Africa, and America, reported thence to England, reduced and printed in three months and one week after its occurrence: "tantum series juncturaque pollet." The returns from the different stations showed that these disturbances were general; that, though the movements individually might not be, and in fact were not, always simultaneous, the observations on the same day never failed to exhibit unusual discordances at all the stations, and were generally characterised by the diminution more or less of the horizontal intensity, prevailing more or less for several hours everywhere, and the movement of the north end of the needle towards the west. Besides the colonial observatories, these phenomena were watched with great attention at the observatories of Prague, Munich, and Greenwich. The report next noticed the new magnetic instruments and modes of observation. We can only enumerate the former, viz. the transportable magnetometer, Dr. Lloyd's induction inclinometer, Weber's inductive inclinometer, and another method proposed by Dr. Lamont. The report next enumerated the publication of various magnetic observations. The only expense incurred by the Association during the year, was £10 18s. 10d., for observa

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tory registers, and the committee prayed a continuance of their grant. Sir John Herschel stated, that the committee for revising the nomenclature of the stars deferred reporting till the catalogue of stars, now in preparation under the auspices of the Astronomica! Society, was ready for publication; and that the committee for the reduction of meteorological observations, in consequence of the illness of Mr. Birt, had been unable to make any considerable progress. The Rev. Dr. Scoresby, "On Improved Permanent Magnets, and the Modes of determining their Powers, with certain undescribed Phenomena in Permanent Magnets."-Dr. Scoresby exhibited a powerful, though moderately sized magnet, as a proof of the practical nature of his researches; and, after some explanations respecting the quality and temper of the metal in magnetized bars, he stated, that when his Researches (now in the press) on the Magnetic Power of the various denominations of Steel, &c., shall be completed, he will be able to determine, at once, and unequivocally, the proper kind and temper of steel, suited to a needle of any given size, and for any specific purpose.

Prof. Lloyd said, that Dr. Lamont, of Munich, was following out a similar course of investigation. M. Nobili had endeavoured to ascertain the constitution of permanent magnets.

Col. Sykes "On the Meteorology of the Province of Coorg in the Western Gâts of India."-The capital of Coorg stands at an absolute elevation of 4,500 feet, and the barometrical observations made there show the same hoary variation or semi-diurnal oscillation of the atmosphere which Humboldt had observed in South America, Col. Sykes in the Deccan, Col. Sabine on the coast of Africa, and which did not wholly disappear, though it diminished in amount, and became hard to detect amid increasing irregularities, in high latitudes.

Mr. Luke Howard produced a chart exhibiting, in curves, the chief meteorological changes observed by him during a cycle of eighteen years. The results of these observations will be found developed and explained in his work on the climate of London.

A letter from Dr. Lamont, director at the Observatory at Munich, was read, stating the names of a great number of professors in Germany, France, Italy, &c., who were aiding in making meteorological observations (commenced seven months ago), so as to present a complete series, extending over the vast tract of country between the Pyrenees and the Russian frontiers. The results are published in the Annalen für Meteorologie, &c.

Sir D. Brewster made a communication "On the Dichroism of the Palladio-chlorides of Potassium and Ammonium."-Dr. Wollaston had found that a long crystal of either of these salts, when looked through transversely, had a green colour, but when looked through from either end, had a red colour; and he (Sir D. Brewster) placed one of these long crystals transversely over another, in a cruciform shape, and then found that those portions of the centres of both, which were in contact, gave a red colour, while all the ends of the crystals were green.

The President then said that a letter had been placed in his hands from Professor Marianini, in Italian, which he had undertaken to translate for the Section; but the heavy duties which devolved upon him during the week completely prevented him. It contained a communication "On the Magnetic Action of Instantaneous Currents of Electricity."

On the Electric Column.

(To be continued).

By J. A. DE Luc, Esq., F.R.S. (Continued from page 90.)

PART III.

Concerning some Meteorological Phenomena, to the better knowledge of which it may lead as an Aërial Electroscope.

WHEN, in our researches, we have in view some great and determined object, we are not only more assiduous in our endeavours to approach it, but more attentive not to be misled in the road, and less disposed to be satisfied with 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.

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 pointed conductors elevated above houses, in hopes to preserve the latter from being struck by thunderbolts. 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 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 insulated 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 or painters, who represent the gods as as sitting on these fogs.

Lightning and thunder, when considered in their true nature, and with all their associated circumstances, though 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 phenomena. 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 as such, must therefore be the consequence of some chemical operation, 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. Besides this immediate consequence of the certain fact, that the quantity of electric fluid 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 decompositions 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.

This is one of the greatest objects that could be offered to the attention of natural philosophers: for it must strike 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

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