That the common varieties of wood which float in water, owe their apparent lightness to air contained in their structure, is generally admitted by those who have paid any attention to the subject. By means of the air-pump, the fact is clearly demonstrated. Under the exhausted receiver, after a certain time, the time varying with the quality of wood, all the different specimens which I have tried have sunk; I may mention two or three in particular, as examples. A piece of oak, weighing 29.7 grs., sank in distilled water, after having been subjected to the air-pump three days;—a piece of deal, weighing 16.3 grs., similarly acted on, floated ten days;—and a portion of the pith of the elder, weighing only .133 grain, floated seven days.

Musket-Bullets are occasionally found inclosed in ivory, and every anatomical museum contains specimens of this kind. Why bullets should be so frequently met with in this situation, it is not easy to say; the head of the animal appears to be generally aimed at, and foreign bodies when they enter the tusks, instead of being removed in the usual manner, are retained by the process, an investigation of which is to form the subject of the present paper.

The minerals of the zeolite family have for many years attracted the especial attention of men of science, and the class has been rapidly extended in proportion to the progress made in its study in a crystallographic as well as chemical point of view. The first characteristic difference, originally observed long since by Cronstedt, and by him considered to be the distinguishing mark of one single mineral species, which he designated Zeolite,—namely, the property of swelling out by heat previous to fusion,—has since been found to belong to a great number of other combinations. These, although materially different from each other in crystallographic form, have proved to be closely allied in chemical constitution, in so far as they consist, without exception, of a silicate of an alkali or alkaline earth, in combination with a silicate of alumina and water. It is evident, then, that the relation of the silicic acid to the base, in both terms, as well as the quantity of water, is capable of considerable variation, so that the general niineralogical formula which should embrace all the members of the zeolite family would be

Where r represents the monatomic alkaline or earthy basis, and the terms u, t, ,T, y, and z, are capable of varying within certain limits.

During the century which has nearly elapsed since Dr Matthew Stewart published his General Theorems, many eminent geometers, both English and Foreign, have attempted to discover their solutions. Those attempts have, however, been rewarded with but limited success, and by far the most general and the most difficult of them remain still without a single published remark in the way of discussion or solution. Dr Stewart did not, as far as I know, make allusion to them himself in any of his subsequent writings, though he describes them as “of considerable use in the higher parts of mathematics;” and we learn from the preface to Mr Glenie's Demonstration of the 42d Proposition (Tract, 1813), that in conversation, Professor Dugald Stewart, in 1805, stated that, “he had not been able to find amongst his father's posthumous papers one word respecting them; that he had, oftener than once, observed mention made of them, in terms of admiration and respect, by some of the first mathematicians on the continent of Europe; but that as both they and the geometers in this country had tried their strength on them without success, and they had so long remained without demonstrations, he never expected to see them demonstrated.” This circumstance, of neither any demonstrations nor even memoranda, on the subject being found amongst Dr Stewart's papers, is readily accounted for by Professor Playfair, in his biography of that distinguished geometer (Edin. Trans. vol. i. p. 74), in the description which he gives of the habits of study of Dr Stewart. “He rarely wrote down any of his investigations till it became necessary to do so for the purpose of publication. When he discovered any proposition, he would put down the enunciation with great accuracy, and on the same piece of paper would construct very neatly the figure to which it referred. To these he trusted for recalling to his mind, at any future period, the demonstration or the analysis, however complicated it might be.”

This phenomenon presented a remarkable interference with those laws which govern the ordinary movements of the ocean. It occurred at one place whilst the tide was flowing, at another whilst it was ebbing; in some cases, producing a sudden retrocession of the waters,—and in others, as sudden an impulse of them on the shore.

The period during which the sea thus continued to retreat and rise respectively, was generally from ten to fifteen minutes. It then made a momentary halt—after which, it began to flow in the opposite direction, and which it continued to do, for about the same period which characterised its previous movement.

In this state of alternate flux and reflux, the sea was at most places observed to continue, for three or four hours together.

The problems on which we were engaged in the preceding Memoir were the following:—1°, The complete determination of the velocity of transmission of a wave in a fluid of any depth, provided the depth is uniform throughout; 2°, an application of the hypothesis of parallel sections to the problem in its more complicated form, in which the depth is variable in the direction of the breadth of the canal; 3°, The investigation of the motion of a solitary wave. We propose in the following pages to continue the same subjects, and to add the more difficult problem of initial motion.

The pleasure which honourable and enlightened minds must feel in acknowledging their obligation to the individuals who have advanced useful knowledge in any department of science,—who have contributed to the means of promoting human happiness, or of alleviating human suffering, has, in all times, led men to seek an opportunity of recording their sentiments of admiration and of gratitude towards the distinguished instructors of mankind. They have felt, too, that the time when one of these guiding lights has been quenched, when a contributor to the treasury of knowledge has just terminated his labours, is peculiarly fitted for the discharge of this duty. The whole amount of his contributions is then presumed to be before them, and they are restrained by no fear of offending his delicacy by their praise, or of having their own feelings hurt by a misconstruction of their motives.

The volatile oil commonly known as Indian-Grass Oil, is supposed by Professor Royle to be produced from a peculiar species of Andropogon. This species he considers identical with the Καλαμος αςωματιχος of the ancient Greeks, an he has therefore called it A. calamus aromaticus.

For the specimen of the oil which I have examined I am indebted to Dr Christison, by whom it was received from Mr Key, of the Madras Medical Service. This gentleman obtained it while resident in the Nizam's territories, not far from Ellichpoor, where the plant grows freely on hilly ground. The oil is there called Roossah-oil.

It was observed by Fahrenheit, that the boiling point of water depends on the height of the barometer, the pressure of the air hindering the conversion of water into steam by a resistance which must be overcome by an increase of heat. Deluc and De Saussure contrived apparatuses for making the observation in the open air, and at great heights, and appear to have contemplated the substitution of the thermometer for the barometer upon occasion. They, as well as Dr Horsley, Sir George Schuckburgh, and Mr Cavendish, seem to have regarded the question as one which concerned the fixity of the point used in graduating thermometers, and its requisite corrections, rather than as applicable to barometric purposes generally.

In 1832 or 1833, a peasant, in felling a tree in the forest about forty miles above Degersfors, laid bare a substance strongly resembling meal, which, tempted by its appearance, he baked with a mixture of rye-flour, and used as bread. “All the world,” says Mr Laing, “of this and the next parish, flocked to the spot to take their part of this extraordinary blessing of meal, produced in the earth at a time when they were reduced to bark bread. The functionaries of the district at last heard of it, and gave orders that it should not be used until they had ascertained that it was safe. Some of it was sent to Stockholm to be analyzed.” Mr Laing has stated, in his Tour, that it was said to consist chiefly of finely pulverised flint and felspar, with a residuum of organised matter; but the proportions, or the regular analysis, he could not learn.

Ever since the discovery by Berzelius of crenic acid in the iron ochre of the water of Porla, in Sweden, chemists have admitted the usual presence of that acid in mineral waters, or those springs containing notable quantities of dissolved inorganic constituents. In such natural waters, also, as are visibly coloured, organic matter is usually understood to be present. Any ideas, however, which may have been entertained respecting the occurrence of organic matter in the perfectly colourless, transparent, and comparatively pure water of ordinary springs, wells, and rivers, have been merely vague and conjectural.

Since my last communication to the Society on this subject, I have continued my experimental investigation of the proposed law which limited the direct action of the voltaic current to the solvent, in solutions of primary combinations of elementary bodies in the more important solvents. All my farther researches have confirmed the rule in regard to aqueous solutions; and I feel now fully convinced of its truth, although, in the mean time, I have had occasion to see a different view advocated by some other experimenters, to whose opinions I shall afterwards advert. Neither have I seen any grounds for altering my views in regard to alcoholic solutions. In regard to ether, some experiments which I shall afterwards mention, have satisfied me that it would be improper at present to include that solvent in any general rule.

In the course of an investigation into the structure and composition of the solid frame-work of vertebrated animals, I remarked, in the vertebral column of cartilaginous fishes, an important peculiarity of structure, which seems to have almost entirely escaped the notice of writers on ichthyology and on comparative anatomy.

Under the name Conversion of Relief, an expression first used by Mr Wheatstone, I include all those optical illusions which take place in the vision of cameos and intaglios, of elevations and depressions, whether they are produced with opaque or transparent bodies,—on surfaces with or without shadows,—in reflected or transmitted light,—while using one or both eyes,—or by erect or inverted vision. In these various forms of the phenomenon, the illusion is modified by certain secondary causes, which were regarded both by Mr Wheatstone and myself as primary causes; so that we were led away, each in a different direction, from the right path of inquiry.

About three years ago, I received from my friend Dr Watt of West Coast, Demerara, specimens of the bark of a tree, native of British Guiana, which had been found by Mr Rodie, late surgeon R.N., to contain a vegetable alkali, and to possess some value as a remedy in the intermittent fevers of that colony. Mr Rodie made known his discovery by means of a letter which he published in the year 1834. I made some experiments with the piece of bark, at that time in my possession; but the conclusions at which I then arrived did not appear to be worthy of being published. It was obvious to me, however, from the results which I obtained, that Mr Rodie's statement was so far correct, that the bark did contain a bitter matter, having all the general characters of a vegetable alkali, and capable of forming neutral compounds with acids. The exhaustion of my original little store of materials prevented me from proceeding farther, till last year, when,through the kindness of Dr Watt, I received a barrel of the bark, and likewise of the fruit of the plant.

The design of the processes described in this memoir was to decompose the bicyanuret of mercury at such a temperature, and under such a degree of pressure, as to secure the simultaneous extrication of the two equivalents of cyanogen, or their elements, in the expectation that they should come off united, and produce the interesting compound of nitrogen and carbon, isomeric with cyanogen, Paracyanogen : And that result was sought in the belief that it would illustrate the chemical theorem of the existence of bodies which, though composed of the same elements in the same proportions, yet differ as widely from each other in chemical properties and mechanical conditions, as one element differs from another.

It is a general belief that Man, in his supposed progress from Savage to Civilized Life, has passed through three distinct stages or periods, each one leading a step forward in the road to social improvement. These stages are asserted to be, 1. The Hunter State; 2. The Pastoral State; and, 3. The Agricultural State. Allusions to these different stages crowd the pages of the historian, the philosopher, and the poet; and arguments are founded on, and deductions drawn from, these states of existence, as if they were ultimate truths, neither to be discussed nor dissented from. It is the object of this paper to question the existence of these separate states, their necessary connection with one another, and the end to which ultimately they are supposed to lead.

In analysing Mr Wheatstone's beautiful discovery, that in binocular vision we see all objects of three dimensions by means of two dissimilar pictures on the retina, I trust I have satisfied the Society that the dissimilarity of these two pictures is in no respect the cause of our vivid perception of such objects, but, on the contrary, an unavoidable accompaniment of binocular vision, which renders it less perfect than vision with one eye. On the other hand, it is quite true that, in Mr Wheatstone's experiment of producing the perception of objects of three dimensions by the apparent coalescence of two dissimilar representations of such objects in plano, the dissimilarity of the pictures is necessary in the exhibition of that beautiful phenomenon.

It seems extraordinary, that no one should have undertaken a geological survey of Roxburghshire, more especially as the counties to the east and west of it have been examined, and accounts of their formations were published some years ago. It cannot be from its uninteresting character, that the intervening district has been neglected; for it presents as great a variety of apparently distinct formations, as there are in the adjoining counties of Dumfries and Berwick; and some of these have long been the special subjects of speculation and controversy among geologists. The British Association, in the Report of its Meeting held at Cambridge in 1833, propounded the following questions for geological inquiry.