The only Theory of the Colours of Natural Bodies that has met with reception in modern times, is that of Sir Isaac Newton, who considers them as identical with those of thin plates, and as varying with the size of the ultimate particles of the body.

Although this theory, ingenious as it is, be liable to many great objections, and be not capable of explaining the phenomena, even if its postulates be admitted; yet the author of the present paper does not assail it with any arguments of this kind. He has, on the contrary, attacked it in its stronghold, and has endeavoured to bring it to the test of direct experiment.

The author undertook the determinations of these positions at the suggestion of Professor Gautier of Geneva, who informed him, that they had not been fixed by any direct observations. The great discrepancies of the best maps of the Alps in laying them down, confirm this opinion; and the author has quoted the latitudes and longitudes, given by the best authorities, at the end of his paper.

The paper began by pointing out the very limited class of bodies to which observations of the kind alluded to have been extended. The author was led to a careful examination of the existing determinations of the conducting powers of the metals for heat, by some collateral trains of experiment in which he was occupied two years ago. He points out the degree of confidence which may be placed in the arrangement of conductors given by different authors; for we appear to be far from reaching a correct estimate of their numerical values. In viewing those of M. Despretz as the best, he remarks, that the position of platinum, which is certainly erroneous, shews how imperfectly we can depend upon experiments on this point, made with even more than usual care. Platinum is placed, by this writer, almost at the top of the list, between gold and silver, whilst the commonest experiments serve to shew that it is really a very imperfect conductor.

The object of the author of this paper, was to shew that the mineral alluded to is not a new atomic compound, but that it consists merely of common sulphate of lead, with a portion of pure sulphur, varying from 6 to 10 per cent.

The object of the author was a careful examination of facts in the Natural History of the Salmon, which hitherto have been taken merely upon opinion. He watched and carefully observed personally the deposition of the ova or eggs of the salmon under the gravel,—its long confinement in that situation,—its growth into a fish about an inch in length,—its ascent through the gravel, and rapid growth whilst in the rivers: the journals of observation were partly read to the Society. Twenty weeks was the period from the time of deposition to their bursting the outer shell; for nine days longer they continued under the gravel as fishes, drawing their nourishment from the yoke of the egg, which is of course attached to them by the umbilical vessels or, more properly, by the ompholo-mesenteric vessels.

The object of this paper, was to describe an example of a class of phenomena, which is imperfectly understood. The author observed an indistinct mass of reflected light, surrounded by a faint glory, on the surface of a stratum of thick white clouds, 1000 or 1200 feet below him, when descending from the Rigi. The centre of the coloured circle was the point diametrically opposite to the sun, and consequently varied with the position of the observer. As he approached the level of the cloudy ocean, the colours became brighter, and the circle more distinctly formed, and the shadows of the author and his companion were thrown with distinct outlines upon the illuminated surface.

The principal object of this paper, was to defend some interpretations of words in the ancient language of Etruria, proposed by Lanzi, and attacked by Niebuhr; as well as to point out some new analogies with other dialects. The languages which the author proposes particularly to call to his assistance are, Greek, Latin, Anglo-Saxon, and Cambrian or Welsh. The paper concluded with an application of these aids to a variety of words in the Etruscan language.

In this paper, the author shewed, by a number of phenomena observable within the coasts of Sweden, chiefly around Stockholm, and on the shores of the Lake Macler and its arms, that the conclusion of the Swedish surveyors in 1821, that a change of the relative level of the land and water along the coasts of the Baltic had in many localities taken place, could not reasonably be disputed.

This paper, composed ehiefly of anatomical details regarding the anatomical structure of the Rorqual, scarcely admits of abridgement. The author has described the skeleton of the cavity for receiving the brain and the mechanism of the larynx at greatest length. The entire length of the whale, measured by a straight line, drawn on the sand from the nose to the middle part of the tail, and making a slight allowance for the curved position in which the animal lay, was 80 feet. Length of the head 23 feet. The girth of the carcass at the pectoral extremities (though the animal had been ten days on the beach, and was much collapsed) 34 feet. Breadth of the tail from tip to tip' 20 feet. The author describes the appearance of the mouth, lined with whalebone, as very surprising.

He demonstrated the navicular bone of the horse's foot not to be a sesamoid bone, nor a peculiar structure formed expressly for the horse, but the Epiphysis of the Os pedis or coffin-bone. This was proved satisfactorily by a direct appeal to structure. Besides anticipating results of practical consequence from this discovery, the author is led to observe, that an organ may be displaced and employed to perform different functions in different animals,—that the epiphyses of bones are intended by nature to form separate bones in a vast variety of animals,—and that they may often lead to the discovery of the type of the skeleton in fossil remains of extinct animals.

The vibrations here referred to, are those which with their accompanying sounds were first observed by Mr Arthur Trevelyan, and communicated to this Society in a paper published in the 12th vol. of their Transactions. The author of the present paper undertook the inquiry as soon as the remarkable fact was announced by Mr Trevelyan, and was induced to prosecute it to a considerable extent experimentally, in consequence of being dissatisfied with the only plausible explanation yet offered,–that of the successive expansions of the cold metal by the hot one at the point of contact at each successive vibration, which was conceived to afford the necessary impulse or maintaining power.

This paper is intended as a necessary supplement to the paper bearing the same title already printed in the Society's Transactions, though but an abridgment of a larger one which the author had prepared on the subject. Particular circumstances induced him to alter the plan he had originally contemplated, and instead of a complete development in detail of his researches and his views, he has only on the present occasion given so much of his results as were necessary to bring the system of polar spherical co-ordinates to a state analogous to that in which plane polar curves has long been stationary, one point of the analogy excepted, viz. where the author has extended the method of treating tangents and normals, and the consequent investigations dependent on these, by giving the polar equations of those lines, instead of merely examining the relation between the radius-vector, and perpendicular upon the tangent. In a note the equations of the tangent and normal, to plain curves, is given from first principles; and the analogy between plane and spherical curves is shewn to be remarkably close.

The object of these experiments was to ascertain some of the circumstances under which the blood changes in colour, from the dark venous to the florid arterial hue.

Dr Stevens first showed, that the venous clot deprived of its serum by washing, remained dark even when in contact with oxygen; and that the addition of a saline solution caused it immediately to become florid. He stated also, that a strong saline solution would cause this change in an atmosphere so highly charged with carbonic acid as to prove rapidly fatal to animals.

The author was led, in prosecution of his researches on the absorptive action of transparent media of light, which have been partly communicated in previous papers to the Society, to examine the influence of coloured gaseous bodies. Iodine vapour was one of these, and its action was found of a similar character to that of fluids having a similar tint. Nitrous acid gas presented a far more extraordinary phenomenon.

The objects proposed by the author of this paper are,—

1. To correct certain opinions prevalent with regard to the membrane of Jacob, this having been frequently comfounded with another, the structure of which forms the immediate subject of the paper.

2. To shew that the Pigmentum Nigrum is not a mere mucus or varnish exhaled by the surfaces on which it is found, but is deposited in a membrane distinct from the choroid, which possesses a peculiar structure hitherto unknown. This membrane, being the seat of the pigment, but not the pigment itself, which may or may not be present, the author proposes to call the Membrane of the Pigment.

This paper described the composition of some crystallized slags from Birtley Iron-Works, in the County of Durham. These slags, like those from Wales described by Professor Miller in the Cambridge Transactions, had the form of the olivine, and in composition were nearly pure silicate of iron, containing about 0.4 per cent, of foreign matter, chiefly magnesia. The author also gave a short account of a method by which the magnet might be made available in giving immediately very near approximations to the quantity of iron contained in the basic silicates of iron.

The author, when he first observed these fringes, found that they presented the appearance of three rectilinear bands, each consisting of black, white, and coloured stripes; but the central band was afterwards found to be composed of two united into one. There is thus a band for each of the four surfaces of the plates, the two side ones, appertaining to the uppermost and undermost surfaces, and the centre ones to the surfaces which are approximated. The peculiarities by which they are distinguished are as follows:—