ture of the ocean and atmosphere, and on the density of sea water. This paper forms part of a journal kept by Dr Davy, in his voyages to Ceylon, and embraces several curious topics of inquiry.

THE ROYAL SOCIETY OF EDinburgh.

January 6th. The Reverend Mr Alison read the second part of his Biographical Account of the Life and Writings of the late Alexander Fraser Tytler, Lord Woodhouselee.

January 13th. The annual meeting was held for the election of officebearers. Lord Glenlee was chosen one of the Vice-Presidents in room of the late Lord Meadowbank; and Professor Jameson, Colonel Imrie, Dr Macknight, and Professor Dunbar, Councillors, in room of Walter Scott, Esq., Dr Jamieson, Dr Brewster, and Mr Bryce, who went out by rotation. January 20th. A paper was read by Thomas Lauder Dick, Esq. on the appearances called the "Parallel Roads" in Glenroy, in the parish of Kilmanivaig, Inverness-shire. Mr Lauder Dick took an opportunity of examining Glenroy in the course of a pedestrian tour which he made to the West Highlands, along with a party of friends, last autumn. In this essay, he describes with great minuteness the appearance of these "roads” or "shelves," (as he is rather disposed to call them,) both when viewed at a distance and upon a close inspection. The whole extent of the glen is about eight or nine miles, extending from north-east to south-west. It consists of six or seven distinct vistas or reaches, into which it is naturally divided by the projections and bendings of the hills which bound it. It is extremely narrow throughout its whole length, and the river Roy runs along the bot.

VOL. X. PART. II.

tom of it. On the sloping surfaces of the hills, on the opposite sides of the valley, the appearances which have been called the "Parallel Roads" present themselves. These are a series of shelves, situated one above the other, which extend throughout the whole glen. In most parts they are three in number; in some parts only_two can be seen; but at one point no fewer than five are distinctly perceptible. From one end of the valley to the other, they preserve the same absolute and relative height, and seem to be perfectly horizontal throughout their whole length. The second road seems to be about thirty yards lower than the first or highest, and the third about sixty yards lower than the second. In number, height, and horizontality, they correspond precisely with each other on the opposite sides of the valley; and this correspondence is preserved round all the bendings, projections, and hollows of the hills. They are various in their depth or breadth at different parts; and are evidently much modified by the nature of the ground. Where the hill forms an acute or rounded promontory, or where it is composed of comparatively soft materials, the shelves are always deep; in a harder soil, their indentation is less; and on the surface of rock, the eye can merely trace them, and that is all. At their deeper and more distinct parts their outer edge may be observed to be considerably rounded off, while they are connected, interiorly, to the acclivity above them, by a highly sloping talus. Their sur face inclines outwards in a slope of about one foot in five; and is almost every where covered with immense blocks of stone, some of them many tons in weight, lying for the most part quite detached on the surface. At the broadest part their surface did not seem to exceed twenty yards.

G

Mr Lauder Dick rejects the hypothesis entertained by some, that these singular shelves are the work of man; and embraces the opinion that they have been produced by the action of the surface of a vast lake, which, at some former period, had filled the whole valley; but which had undergone a series of successive subsidences from the bursting out of its waters, corresponding to the number of "reads" now visible. He has even discovered a point in the glen, through which he conceives the waters may have rushed out when the lake subsided from the level of the first to that of the second "road." He supports this theory by a number of observations made on the margins of deep Highland lakes; and also by a perfectly analogous instance of a horizontal road or shelf which surrounds a valley a little above the town of Subiaco, forty-six miles eastward from Rome; which valley is known to have been at one time filled with water.

The ruins of the Baths of Nero, and the remains of the mouth of the Aque duct by which Appius Claudius conveyed water into Rome, are still to be seen on this horizontal road, which now appears high upon the face of the hills bounding the valley on each side.

Mr Lauder Dick's description was illustrated by sketches and a plan.

January 27th. The following gentlemen were elected members of the Society.

The Right Hon. Earl of Wemyss and March,

The Right Hon. the Lord Advocate of Scotland,

Mr Baron Clerk Rattray,
Lord Reston,

Dr Francis Buchanan, F. R. S. and
F. A. S.

Dr David Hosack, F. R. S. London, F. L. S., and Professor of the Theory and Practice of Physic in the

University of the State of New
York,

John Wilson, Esq. Advocate,
John Fleming, Esq. late President of
the Medical Board of Calcutta,
Dr David James Hamilton Dickson,
James Skene, Esq. of Rubislaw,
Dr William Pultney Alison,
Dr John Howell,
Reverend Robert Morehead,
Robert Bald, Esq., Civil Engineer,
Thomas Sivright, Esq. of Meggetland.

February 3d. A paper, by Dr Brewster, was read, containing an account of experiments made by himself and Dr Gordon, on the human eye. These experiments, which were made upon a very recent eye, related principally to the refractive power of the aqueous, vitreous, and crystalline hu. mours, and to the polarising structure of the different parts of the organ. The aqueous and vitreous humours were found, contrary to the received opinion, to have refractive powers perceptibly greater than that of water, the refractive power of the vitreous humour being the highest. The crys talline lens exhibited a polarising structure, exactly the same as quartz, or one set of doubly refracting crys tals, or the same as the middle coats of the crystalline lens in fishes. (See Philosophical Transactions of London for 1816, p. 311.) The iris had the very same structure, but the cornea had an opposite structure, nearly the same as that of calcareous spar, or the

same as the outer and inner coats of the crystalline lens in fishes. The tint po. larised by the human crystalline was a faint blue of the first order.

At the same meeting, the Reverend Dr Brunton read a paper, written by Dr Craigie, on the Affinity between the Persian, and the Greek and Latin Languages.

Sir George Mackenzie read an extract of a letter from Thomas Allan,

Esq. containing a sketch of the mineralogical structure of the country round Nice. It is composed almost wholly of limestone, the strata of which are disposed in the most irregular manner. They enclose shells of the same description with those which are found in the sea beneath.

February 17th. Sir George Mackenzie read the first part of an Essay on the Theory of Association in Matters of Taste.

This paper was intended to be read at the meetings of 3d and 17th March, and has since been published in a se parate form.

April 7. Mr Campbell read a paper on the theory of vision. He stated the opinions of Dr Reid, Paley, and philosophers in general, to be, that the sensation of vision is produced by pictures painted on the retina, pictures similar to those which may be formed on the hands or the cheek, by means of proper glasses. This opi nion he opposed, on the ground that no such pictures are formed on the human eye, the retina being so transparent, as to transmit all the rays of light, and these, when they have passed through the retina, being all absorbed by the choroides. He proposed, as an explanation of the problem, the following theory. Vision consists in two kinds of perception-the discrimination of dimensions and figure, and the discrimination of colour. In discriminating dimensions and figure, the eye obtains information similar to the organ of touch, an assemblage of rays, corresponding exactly in figure and relative dimension to the body seen, penetrating the retina, and exciting there a corresponding area of the optic nerve. In discriminating colour again, the power is more analogous to that of the organs of smell and taste. The different coloured rays having peculiar modes of affecting the retina, excite the area differently, according to

these peculiar modes; an excitement is thus produced on the retina, or optic nerve, by which it communicates information to the mind, and intimations of the figure and colours of visible objects.

A paper from Dr Murray was read, on the means of obviating the risk of explosion in the newly invented blowpipe of Mr Brooke. The difficulty that has been found in the methods formerly employed, of having two separate reservoirs, is that of adjusting the issue of the gases in the requisite proportion of two volumes of hydrogen to one of oxygen, a difficulty, which, by any adjustment of pressure, or of area of tube, is not easily obviated.

Dr Murray, conceiving that the method of having two reservoirs, must always be superior in safety to that of having the gases mixed in a single servoir, thought of obviating this difficulty by forming a combustible mixture, the volume of which would be equal to that of the oxygen necessary for the combustion. Such a mixture is obtained by the addition of a requisite proportion of olefiant, or of coal gas. From the results of some experiments, the heat produced by such a mixture, seemed scarcely equal to that with pure hydrogen; but the experiments had not been brought to such accuracy as to render it certain, that this might not be owing to some adventitious circumstances.

Dr Murray also proposed another method which, on the whole, he thought preferable, in which pure hydrogen is used, that of having three reservoirs fixed down on a board by a cross bar, one of oxygen with one of hydrogen on each side, connected with a tube from each, with stop-cocks, and terminated in a common tube, fitted also with a stop-cock. The gases would thus be easily presented to one another in the requisite propor

tion, and all the risk completely obviated.

April 21. A paper, by Dr Brewster, was read, containing an account of some new properties of light and of crystallized bodies, which he had lately discovered; some of these properties were exhibited before the society. At the same meeting, a paper, by Dr Trail of Liverpool, was read. It contained an analysis of a new mineral substance which he found at Stromness, in the Orkney Islands. It consisted of a sulphate of barytes and carbonate of strontian : but it did not appear to be ascertained that these ingredients were in a state of chemical combination. Dr Trail proposed to call the mineral Stromnessite, from the place where it was discovered, or Bary. strontianite, from its composition.

May 5. Dr Hope exhibited to the society an improvement upon the new blow-pipe, by which it is rendered perfectly secure from explosion. This improvement consisted in interposing about one hundred folds of wire-gauze between the reservoir which holds the gases, and the mouths from which they issue.

At the same meeting, Dr Dewar exhibited a specimen of a phial which he proposes for preserving volatile and deliquescent substances accurately from communication with the surrounding air, by means of mercury. The phial was made with a deep rim round the shoulder, which was intended to contain a small quantity of mercury, and into this, the mouth of an inverted glass cover, enveloping the mouth and stopper of the phial, was to be immersed. This apparatus, Dr Dewar conceived, would contribute materially to the convenience of the practical chemist, the druggist, and others, in a considerable variety of instances.

On the 19th, a paper, by Mr Stevenson, civil engineer, was read, regarding the operation of the waters of

the ocean and of the river Dee, in the basin or harbour of Aberdeen; from which it appears, that Mr Stevenson, in the month of April, 1812, with the use of an instrument, (of which he exhibited a drawing,) has been able to lift salt water from the bottom, while it was quite fresh at the surface, and has satisfactorly ascertained that the tidal or salt water keeps in a distinct stratum or layer, under the fresh water of the river Dee. This anomaly, with regard to the salt and fresh waters, appears in a very striking manner at Aberdeen, where the fall of the Dee is such as to cause the river water to run down with a velocity which seems to increase as the tide rises in the harbour, and smooths the bed of the river. These observations shew, that the salt water insinuates itself under the fresh water, and that the river is lifted bodily upwards; thus producing the regular effect of flood and ebb tide in the basin, while the river flows downward all the while with a current which, for a time, seems to increase as the tide rises.

These facts, with regard to the continual course of the river Dee downward, is such a contrast to the operations of the waters of the Thames, as seen by a spectator from London bridge, that Mr Stevenson was induced to extend his experiments to that river, in the years 1815 and 1816, by a train of experiments and observations from about opposite to Billingsgate all the way to Gravesend. The waters of the Thames opposite the London Dock gates were found to be perfectly fresh throughout; at Blackwall, even in spring tides, the water was found to be only slightly saline; at Woolwich, the proportion of salt water increases, and so on to Gravesend. But the strata of salt and fresh water are less distinctly marked in the Thames than in any of those rivers on which he has hitherto had an opportunity of making his

observations. But these inquiries are meant to be extended to most of the principal rivers in the kingdom, when an account of the whole will be given. From the series of observations made at and below London bridge, compared with the river as far up as Kew and Oxford, Mr Stevenson is of opinion, that the waters of the Thames seldom change, but are probably carried up and down with the turn of the alternate tides, for an indefinite period, which he is of opinion may be one, if not the principal cause of what is termed the extreme softness of the waters of the Thames,

Mr Stevenson has made similar experiments on the rivers Forth and Tay, and at Loch Eil, where the Caledonian Canal joins the Western Sea. The aperture at Curran Ferry for the tidal waters of that loch, being small compared to the surface of Loch Eil, which forms the drainage of a great extent of country; it therefore occurred to Mr Stevenson, that the waters of the surface must have less of the saline particles than the waters of the bottom. He accordingly lifted water from the surface at the anchorage off Fort William, and found it to be

1008.2

1025.5

At the depth of 9 fathoms, At the depth of 30 fathoms in the central parts of the loch it was 1027.2 Indicating the greater specific gravity, and consequently more of the saline particles, as the depth of the water is increased.

At the same meeting, a notice, by Dr Brewster, was read. It relates to the discovery of a general principle respecting forces which emanate from the axes of doubly-refracting crystals. June 2. The Reverend Mr Morehead read a paper entitled, Observations on the Agamemnon of Eschylus, illustrated with Translations.

At the same meeting, Dr Gordon

communicated an account of the circumstances attending a narrow escape which Mitchell, the blind and deaf boy, had made from being drowned.

16. Mr Morehead concluded his Observations on the Agamemnon of Eschylus.

A communication on the laws of double refraction and polarisation, by Dr Brewster, was laid before the society.

The meetings of the society were adjourned till the 1st of November.

THE LINNEAN SOCIETY.

ON Tuesday, Dec. 3, a description was read of fossil belemnite on flint, by Dr Arnold. The specimen was remarkable, because it exhibited a very distinct jointed syphunculus passing through the fossil. Very little is known respecting the nature of the animal that inhabited this fossil. Dr Arnold conceives that it was capable of rising or sinking in water at pleasure, and that its structure was somewhat similar to that of the nautilus or cornu ammonis.

At the same meeting, several specimens of an unknown fossil in flint, sent by Dr Arnold, were exhibited. They consist of small flat spherical bodies, having a pression in the centre, in which is a small tubercle, so as to give an appearance somewhat similar to a small acorn before it is ripe, and while still in its cup. Each of these spherical bodies sends a vessel into each of the spheres that surround it, so that the fossil resembles a kind of net-work, The usual size of the spheres is rather less than a peppercorn, and the vessels are as fine as hairs. No name has hitherto been given to this fossil. the same meeting, a specimen of an unknown fungus from Virginia, sent to the society by Dr Mitchell, was exhibited. It was very heavy, white,

At