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seven experiments of his own, thus made, and two of M. De Luc's, he found that the results followed a law, from which they differed, at a medium, not more than 1-10th of a degree. This law is, that the square of the temperature of a given portion of gas, varies as the elasticity and volume conjointly; and, therefore, when either continues the same, the temperature is as the square root of the other. Hence Mr H. found, that the heat of boiling water is to that of melting ice, as the 11 to the 8, or as 1.1726 to 1 nearly; and the point of absolute cold he also determines in a manner inde pendent of any theory of heat, from the principle of an air thermometer.

In June nothing of any particular interest was communicated to the Society; and in July, the only paper we shall notice, was communicated on the 12th, and entitled, " On a New Compound of Chlorine and Carbon," by Messrs Phillips and Faraday. This compound was brought to England, and given to these gentlemen by M. Julin, of Abo, in Finland. It was formed during the distillation of green vitriol and nitre, for the production of nitric acid; is of a solid crystalline body, fusible and volatile by heat,

without decomposition; is insoluble in water, but soluble in alcohol, ether, and essential oils; sinks in water; burns with a red flame, giving off much smoke, and fumes of muriatic acid gas; is not acted upon by acids; and gives out chlorine, and deposits charcoal, when its vapour is heated in a tube till decomposition takes place. Potassium burnt with it, forms chloride of potassium, and liberates charcoal; its vapour, detonated with oxygen over mercury, forms carbonic acid, and chloride of mercury; passed over hot oxide of copper, it constitutes a chloride of copper and carbonic acid; and over hot lime, it occasions ignition, and produces chloride of calcium, and carbonic acid. It is composed of chlorine and carbon, and, from the experiments detailed, two parts appear to be formed of

1 portion of chlorine.. 44.1..33.5 2 portions of carbon.. 15.0..11.4 Hence it is a sub-chloride of carbon. All attempts to form it by other means have hitherto failed.

After hearing another paper, by C. Bell, Esq., on the Structure and Functions of the Nerves, read, the Society adjourned till the usual period.

THE ROYAL SOCIETY OF EDINBURGH, 1820-1.

AFTER the usual adjournment, this Society resumed its sittings on the 15th of November, 1819, when a paper, by Dr Brewster, was read, on the subject of Circular Polarization, a name by which he proposed to distinguish the phenomena first discovered by M. Arago, along the axis of rock crystal, afterwards analyzed by M. Biot, and

subsequently discovered by MM. Biot and Seebeck in several fluids. M. Biot had shewn, that, in some specimens of rock crystal, a certain succession of tints was produced, by turning the analyzing prism direct from right to left, while, in other specimens, the same succession was developed by turning the prism in a retrograde di

rection, from left to right. He detected a similar difference in fluids; and he concluded that the cause of the phenomena resided in the ultimate particles of silex and the fluid, and was entirely independent of their mode of aggregation. The principal object of Dr B.'s paper was to describe the co-existence of the direct and retro grade structure in the same mineral, and the entire extinction of the circular polarization in the stratum which intervened between the two opposite structures. He discovered traces of circular polarization in crystals with two axes, and detected some new properties of this remarkable species of polarization. Several arguments were adduced to shew, in opposition to the opinion of Biot, that, in the case of crystals, or of solid bodies dissolved in fluids, the property of circular polarization cannot belong to the ultimate particles.

Office-bearers and counsellors for the ensuing year were elected on the 29th.

On the 6th of December a paper was read, containing further particulars respecting the celebrated slide at Alpnach, with a notice of its recent demolition. Referring, for full and satisfactory information, to Professor Playfair's interesting description of this remarkable work, which the reader will find in the recent edition of his works, we need only mention that this slide was formed upon the side of Mount Pilatus, in the canton of Unterwalden, by MrJohn Rupp, engineer, for the purpose of bringing down the valuable timber, with which the mountain was covered, into the Lake of Lucerne, from which the conveyance to the German Ocean was easy and expeditious. It was constructed of about 25,000 large pine-trees, deprived of their bark, and united together in a very ingenious manner, without the aid of iron, It occupied 160 workmen

during 18 months, cost nearly 100,000 francs, or 42504, extended about three leagues, or 44,000 English feet, and terminated in the Lake of Lucerne. It had the form of a trough, about six feet broad, and from three to six feet deep; its bottom was formed of three trees, the middle one of which had a groove, cut longitudinally, for receiving small rills of water, conducted into it from various places, for the purpose of diminishing the friction; and the whole of the slide was sustained by about 2000 supports, and in many places attached, in a very ingenious manner, to the rugged precipices of granite. The direction was sometimes straight, and sometimes zig-zag, with an inclination of from 10° to 18°; it was carried along the sides of hills, and the ranks, and sometimes the summits, of precipitous rocks; in some places it passed under ground, and in others was conducted over deep gorges by scaffoldings 120 feet in height. In the progress of the work the greatest difficulties were encountered and overcome by zeal and perseverance. When finished, it was found to answer every purpose for which it had been intended.

Large pines, about 120 feet in length, and ten inches in thickness at their smaller extremity, darted through the space of three leagues in 2 minutes, and, during their rapid descent, appeared to be only a few feet in length. In order to shew the enormous force acquired by the trees from the velocity of their descent, M. Rupp made arrangements for causing some of them to spring from the slide. They penetrated, by their thickest extremities, no less than from 18 to 24 feet into the earth; and one of them having by accident struck against the other, it instantly cleft it through its whole length, as if it had been struck by lightning. After the trees had descended the slide, they were collected into rafts upon the Lake, and conduct

ed to Lucerne. From thence they descended the Reuss, then the Aar, to near Brugg, afterwards to Waldshut, by the Rhine, then to Basle, and, lastly, to the sea, when it was necessary. We regret to add, that this magnifi. cent structure no longer exists, scarce ly a trace of it being to be seen on the flanks of Mount Pilatus. Political cir. cumstances having destroyed the principal source of the demand for the timber, although large and of excel lent quality, the operation of cutting and transporting the trees has necessarily ceased.

On the 3d and 17th of January, 1820, Dr Ferguson, inspector of hospitals, read a very interesting paper on the Nature and History of Marsh Poison, as known under the titles of Marsh Miasmata and Malaria. From a reference to the medical topography of various places in the south of Europe and the West Indies, the author endeavoured to prove, that the universally received opinions of aqueous and vegetable putrefaction, single or combined, being the sources of this poison, were unfounded; that putrefaction, under any form, had no effect in producing it; that it never emanates from water, however putrid, nor is necessarily an exhalation from marshes; but, on the contrary, some peculiar modification of the atmosphere by heat and moisture, being the product of a highly advanced stage of the drying process in absorbent soils, which had previously and recently been saturated by water. In support of this opinion, the author stated the following among other remarkable facts: In the course of the Peninsular War, during the autumnal campaign of 1808, our troops, after the battle of Vimeira, were comparatively healthy. The soil of the province around Lisbon, where they were quartered, is a very healthy one-a slight covering of light and sandy soil, on a substratum of hard

rock, which is almost always so bare, that water can seldom be absorbed into it to any depth, but is held up to speedy evaporation. The season was fully as hot a one as is ordinarily seen in that country, but dysentery was the prevailing disease. Early in 1809 the army advanced to Oporto, for the expulsion of the French, under Marshal Soult, from Portugal; which, during a very cold and wet month of May, (for that country,) they effected, without suffering any diseases but the ordinary ones of the bivouac; and in June, advanced again towards Spain, in a healthy condition, during very hot weather. The army was still healthy, certainly without endemic fever, and marching through a singularly dry rocky country, of considerable elevation, on the confines of Portugal. The weather had been so hot for several weeks as to dry up the mountainstreams; and in some of the hilly ravines, that had lately been watercourses, several of the regiments took up their bivouac, for the sake of being near the stagnant pools of water that were still left among the rocks. The staff officers who had served in the Mediterranean, pointed out the dangerous nature of such an encampment; but as its immediate site, amongst dry rocks, appeared to be quite unexceptionable, and the pools of water in the neighbourhood perfectly pure, it was not changed. Several of the men were seized with violent remittent fever, before they could move from the bivouac the following morning; and that type of fever, the first that had been seen on the march, continued to affect that portion of the troops exclusively for a considerable time. Till then, it had always been believed amongst us, that vegetable putrefaction (the humid decay of vegetables) was essential to the production of pestiferous miasmata; but, in the instance of the half-dried ravine before us, from the stony bed

of which (as soil never could lie for the torrents) the very existence of vegetation was impossible; it proved as pestiferous as the bed of a fen. The army advanced to Talavera, through a very dry country; and, in the hottest weather, fought that celebrated battle, which was followed by a retreat into the plains of Estremadura, along the course of the Guadiana river, at a time when the country was so arid and dry, for want of rain, that the Guadiana itself, and all the smaller streams, had in fact ceased to be streams, and were no more than lines of detached pools in the courses that had formerly been rivers; and then they suffered from remittent fevers, of such destructive malignity, that the enemy and all Europe believed that the British host was extirpated; and the superstitious natives, though sickly themselves, unable to account for disease of such uncommon type among the strangers, declared they had all been poisoned by eating the mushrooms, (a species of food they hold in abhorrence,) which sprung up after the first autumnal rains, about the time the epidemic had attained its height. In all the subsequent campaigns of the Peninsula, the same results uniformly followed, when ever, during the hot seasons, any portion of the army was obliged to occupy the arid encampments of the level country, which, at all other times, were healthy, or at least unproductive of endemic fever."

Other properties of the marsh poi. son, such as its particular attraction for, and adherence to, lofty umbrageous trees and rising grounds in the neighbourhood of swamps; its concentration in ravines, hollows, or lee

ward localities; its absorption from passing over water, and rarefaction or dissipation by the sun's heat, and regular currents of wind, were also pointed out and illustrated by a detail of facts, observed by the author during his service in the Peninsula and the West Indies. In the course of the paper, and while treating of the effect of the marsh poison, the author was led to consider its extreme and most baleful product, the yellow fever of the tropics, the non-contagious nature of which was established by a series of facts and arguments that appear to be completely conclusive. The highest degree of susceptibility and excitement from solar heat, on the part of the subject, combined with the highest state of preparation from the same, on the part of the agent, appear to be essential in all situations to the production of the dreadful yellow fever, which, luckily for mankind, is incapable of being transported to any locality of lower temperature, or texture of soil different from that which gave it birth. In conclusion, the author made some observations on the mode in which the marsh poison is received into the human constitution, whether by the lungs, the stomach, or the skin; which last, the author seemed to think, was the most probable channel, and supported this opinion by some illustrations taken from the plague in the Levant, and the peculiar idiosyncracy of the African or Creole negroes, to whom the marsh miasmata are, in fact, no poison.

On the 7th of February, a paper by Dr Brewster was read, on the Mean Temperature of the Earth. The object of this paper was to explain a new

During the years 1815, 1816, and 1817, Dr Ferguson was employed to make a topographical health survey of all the West India colonies, which afforded him opportunities of the most favourable kind of improving the observations he had elsewhere made upon pestiferous miasmata.

and simple formula, for finding the mean temperature of any place in the western region of the Old World, in all latitudes, and to point out its remarkable accordance with the fine series of observations collected and arranged by M. Humboldt. The formula given by the Doctor was,

T-81.5° Cos. L.

T being the temperature at the level of the sea, in degrees of Fahrenheit's scale, L the latitude of the place, and 81.5° the mean temperature of the equator, as deduced by Humboldt. This formula gives, to a remarkable degree of exactness, the mean temperature of the parallel of 78° in the Greenland seas, as ascertained from numerous observations by Mr Scoresby; and from its coincidence with observations at the equator, in the parallel of 45°, and in the Arctic regions, there can be little doubt that the mean temperature of the North Pole differs very little from 0° of Fahrenheit, in place of 32°, as assumed by Mayer and others. The formula of Mayer errs no less than 9° in latitude 78°. The paper was accompanied with a table of the ascertained mean temperature of thirty-one places, compared with the new formula, and with that of Mayer; the sum of the errors of the former being 76.73°, that of the latter only 26.41°.

Nothing calling for particular notice in this place, occurred till the 15th of May, on which day, Dr Duncan, sen., read a Biographical Account of the late Dr Daniel Rutherford. Dr R. was born at Edinburgh on the 3d of November, 1749. He took his degree of M.D. in 1772, on which occasion the subject of his Thesis was De Aere Fixo. In this dissertation he pointed out, for the first time, a new gaseous substance, since distinguished by the name of azote, or nitrogen. He was admitted a Fellow of the Royal Col

lege of Physicians, on the 6th of May 1777. In a paper on Nitre, read before the Philosophical Society in 1778, he described, under the name of vital air, what is now called oxygen gas; considering its basis as a necessary constituent of every acid, and even stating it as not improbable, that by this element they were acid. On the death of Dr John Hope, in 1786, he was elected Professor of Botany, and Keeper of the Botanic Garden; a duty which he discharged till the time of his death, which took place on the 15th of November, 1819, in the seventy-first year of his age.

On the 1st of June, an Abstract of a Mathematical Paper, by Professor Wallace, was read. In the year 1808, Mr Wallace communicated to the Royal Society, a paper on the Quadrature of the Conic Sections, and the Computation of Logarithms, which was published in the sixth volume of its Transactions. In that paper, general expressions for the reciprocal of any elliptic or hyperbolic sector; likewise for the reciprocals of its second and third power; and analogous expressions were investigated for the reciprocals of the powers of the logarithm of a number. These were found by principles at once simple and elementary, without any reference to the differential, or other equivalent calculus; and, unlike the ordinary series, which, in some cases, converge too slowly to be of any practical use, they are always applicable. In the paper to which this notice refers, the same elementary principles are applied to the investigation of new series, for the simple powers of the areas of elliptic and hyperbolic sectors, and for the logarithm of a number; and these are at once simple and symmetrical in their number, and universally applicable. From the general expression for the area of the sector of any conic section, we derive the following for the arc of a circle:

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