and the vegetable matter of fuci. The materials were boiled together, and then left for a longer or shorter time till consolidation took place.

As gypsum, which was used in most of these experiments, does not occur in the strata supposed to have been possibly consolidated by the action of animal and vegetable matter, the author, to ascertain whether gypsum might be dispensed with, employed pure magnesia, and with success. Specimens of consolidated magnesia were shewn. From some other experiments, the author is inclined to believe that animal matter, fossilized in the centre of a mass containing lime, attracts to itself the lime from the general mass.

Further experiments must determine how far the observations of the author are capable of being applied to explain any part of the phenomena of the consolidation of strata, or of the fossilizing of organic remains.

The following Gentlemen were duly elected Ordinary Fellows of the Society :—

Dr TAYLOR, of Pau.

Dr PAGAN, F.R.C.S., Edinburgh.

The following Donations to the Library were announced: Recueil des Actes de la Séance Publique de l'Académie Impériale

des Sciences de Saint Petersbourg, tenue le 29 Decembre 1844. Memoires de l'Académie Impériale des Sciences de Saint Petersbourg (Sciences Politiques, &c.) Tome V., Livres 5 and 6. Memoires de l'Académie Impériale des Sciences de Saint Petersbourg (Sciences Mathematiques, &c.) Tome IV., Livres 6. Memoires de l'Académie Impériale des Sciences de Saint Petersbourg (présentés par divers Savans.) Tome IV., Livres 6.By the Academy.

Catalogue of the Edinburgh Subscription Library, 1794–1846.— By the Office-Bearers of the Library.

Journal of the Statistical Society of London. Vol. VIII., Part 4.— By the Society.

Proceedings of the Geological Society of London. Vol. IV., No. 104. -By the Society.

The Journal of Agriculture, and the Transactions of the Highland and Agricultural Society of Scotland. January 1846.-By the

Society.

Journal of the Asiatic Society of Bengal, Nos. 146 and 147.—By the Society.

The Derivation of many Classical proper Names from the Gaelic Language, or the Celtic of Scotland. By Thomas Stratton, M.D.-By the Author.

Monday, 19th January 1846.

Right Rev. BISHOP TERROT, V.P., in the Chair.

The following Communications were read:

1. On the Action of Soluble Lead Salts on Natural Waters. By Professor Connell.

In a former communication to the Society, the author noticed that spring, well, and river waters, even after being boiled, usually yield, with acetate of lead, a precipitate readily soluble, in whole or great part, in acetic acid; and as the solution appeared not to be attended with effervescence, it was conceived to be due to organic matter. The author has since found that effervescence is more common than was at first supposed, and in that case the precipitate is due to the presence of carbonate of lime in the water. It was ascertained by boiling a solution of carbonate of lime in water containing excess of carbonic acid, that the trace of carbonate of lime retained in solution after ebullition, was too slight to explain the reaction of the spring waters, on the idea that it had been originally taken up by them in this way. It was farther found that distilled water, when left in contact for several days in a close vessel with impalpably pounded marble, took up a very little more; but what the author conceives to be the more probable source of the carbonate of lime in the spring waters is double decomposition between a soluble lime-salt and a carbonated alkali. The reaction may be imitated by adding to an ounce of distilled water one drop each of carbonate of potash, muriate of lime, and sulphate of magnesia, when acetate of lead will be found to yield a cloud like spring waters,

soluble with effervescence in acetic acid. When the precitate in the spring water is truly dissolved without effervescence by acetic acid, it is due to organic matter, provided no chloride is present in sufficient quantity to produce the reaction.

2. Claudia and Pudens; an attempt to shew that the Claudia mentioned in St Paul's Second Epistle to Timothy, was a British Princess. By Archdeacon Williams.

The following Donations to the Library were announced:Third Bulletin of the Proceedings of the National Institute for the Promotion of Science at Washington. February 1842 to February 1845.-By the Institute.

Tenth Letter on Glaciers.-By Professor J. D. Forbes.

Notes on the Topography and Geology of the Cuchullin Hills in Skye, and on the Traces of Ancient Glaciers which they present. By Professor J. D. Forbes.-By the Author.

Journal of the Asiatic Society of Bengal. No. 158.—By the Society.

The Electrical Magazine. Conducted by Mr Charles V. Walker. October 1845.-By the Editor.

The Journal of the Royal Geographical Society of London. Vol. XV., Part 2.-By the Society.

Bulletin de la Société de Geographie. Tome III., of 3d Series.By the Society.

Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin. 1843.

Bericht uber die zur Bekanntmachung geeigneten Verhandlungen der Konigl.-Preussische Akademie der Wissenschaften zu Berlin. Juli 1844 bis June 1845.-By the Academy. Novorum Actorum Academiæ Caesarea Leopoldino-Carolina Naturæ Curiosorum voluminis decimi noni Supplementum et volumen vigesimum.—By the Academy.

Scheikundige Onderzoekingen gedaan in het Laboratorium der Utrechtsche Hoogeschool. Deel III., Stuk. 3.—By the Edi

tors.

Monday, 2d February 1846.

Sir T. M. BRISBANE, Bart., President, in the Chair.

The following Communications were read :

1. On the Decomposition and Dispersion of Light within Solid Bodies. By Sir David Brewster, K.H.

After noticing various cases of solid and liquid bodies, which disperse light of a colour quite different from the transmitted tint, and Sir John Herschel's explanation of the phenomenon in the solution of acid sulphate of quinine, which, although itself colourless, disperses light of a bright blue, the author considers

1. The internal dispersion of fluor-spar. By employing a more intense light than Sir J. Herschel did—namely, a condensed beam of the sun's light-he conceives that he has proved that the dispersion is not, as Sir J. Herschel supposes, superficial or epipolic, but, on the contrary, belongs, in some specimens at least, to every part of the crystal. The phenomenon is only seen in the green fluor of Alston, and in some pink and bluish-yellow varieties from Derbyshire. Some specimens are formed of strata alternately dispersing and non-dispersing. The author has not found the same appearances in any other mineral; but he has observed similar phenomena of dispersion in several kinds of glass, and even in some colourless glasses, which disperse a fine green tint.

2. On the internal dispersion of the acid solution of sulphate of quinine. Here, also, by using a more intense light than Sir J. Herschel, the author establishes that the peculiar dispersion occurs, not only in a stratum 1-50th of an inch thick at the surface of the liquid, but at all parts of it; and he concludes —First, That a beam of light, epipolised by the action of a solid or a liquid, is capable of further dispersion, provided the thickness of the medium has not been sufficient to disperse all the dispersible rays. Secondly, When such a medium is thus rendered incapable of dispersing more light, it is not, as Sir J. Herschel supposes, because the light has lost a property which it previously possessed, but because it has been deprived of all the dispersible rays it contained.

The rays thus dispersed are few in number, and, by their mixture, yield blue light, but they extend over a great range of refrangibility; while other rays, equally refrangible, are either less dispersible, or not dispersible. But this appears less surprising when we advert to the phenomena of absorption.

The difference between absorption and dispersion is, that, in the former case, the absorbed light is extinguished; while, in the latter, the dispersed light is visible. Hence, if, in powerfully absorbing bodies, the absorbed light could be rendered visible, we should have the phenomena of epipolised light.

3. On the polarisation of dispersed light. Sir J. Herschel had failed to detect the polarisation of epipolised light; but the author, by using a condensed sunbeam, discovered that the dispersed beam was polarised, partly in the plane of reflexion, and partly in a peculiar manner; which the author calls quaquaversus polarisation, like that effected by a congeries of small doubly-refracting crystals, having their axes in all directions. He afterwards discovered instances in which each of these kinds of polarisation was found alone. These experiments have led to more extended investigations, to be subsequently communicated. The remainder of the section contains a minute description of the beautiful phenomena of the polarisation of dispersed light. The author thinks it probable that the study of these phenomena may throw much light on the internal structure of the substances exhibiting them.

4. On the causes of the decomposition and internal dispersion of light. The author ascribes the phenomena (which do not, in fluorspar, belong to the species, but only to certain varieties) to irregular crystallisation, and the successive deposition of strata of different refractive and dispersive power. He does not, at present, offer any theory of the cause in liquids.

2. A few Remarks suggested by Professor Forbes's Description of the effects of Glacial Action among the Cuchullin Hills, and Mr Maclaren's views of the facts observed by him at the Gareloch. By Sir G. S. Mackenzie, Bart. The object of this paper was to shew, that if it be assumed that glaciers had actually existed among the Cuchullin Hills, or in other parts of this country, one of two conditions must necessarily have been present either a climate much colder than the existing climate of Scotland, or a higher position of the land where the supposed marks of glaciers are seen. With respect to the first condition, the permanency of the relative positions of the heavenly bodies, and of the inclination of the earth's axis, and the adaptation to existing climates of animal and vegetable life, were appealed to

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