stood in the line of its intended removal, the Dewan was obliged to contract his views as to its height. The column was quarried about two miles from the place where it was erected. This was effected by first cutting a groove in the rock about two inches in width, and the same in depth, and then inserting, at intervals, small chisels, on which the workmen kept beating with iron mallets from right to left, or from left to right, till the separation was completed. The obelisk was first blocked out in the rough to lighten it before being placed on its carriage, by means which will be easily conceived after describing those used for its erection. The carriage, after repeatedly sinking into the hard road as into a swamp, was ultimately moved over a succession of balks of timber placed for its support. Granite is so excessively brittle, that it was thought hazardous to employ draught cattle, or any power less manageable than that of men; and Colonel Wilks thinks about 600 were required at a time for the drag-ropes. The operation of removing so vast a mass was, as might naturally be expected, extremely tedious; but the patience and perseverance of the natives surmounted all obstacles.

The most difficult part of the process however remained, namely, after the shaft was finished, and placed in a horizontal position raised to the proper height, with its base fitted for insertion into the top of the pedestal, to bring it to the vertical position, and insert the lower end of the shaft in the cavity prepared for its reception. This shall be described in the words of Colonel Wilks, who was an eye-witness of the operation. "Imagine," says he, "a strong wall, built at right angles with the line of the shaft, and a few feet beyond its smaller end; with two lateral retaining walls parallel to the shaft, and a fourth of smaller elevation near the pedestal, to support the

mass of earth and the workmen to be employed. On such a platform, raised 10 feet, you will, in the first instance, conceive the shaft to be ho rizontally arranged. Two lines of timber, plank or balk, were then ranged along the two sides of the shaft to serve as fulcra, and two lines of men, with handspikes, attended by others ready with chocks, or pieces of timber of different thickness to be inserted under the shaft, for the purpose of keeping the elevation of the smaller end, effected by the handspikes, and distributing the pressure so equally, as not to risk the accidents which would otherwise be inevitable with this very fragile substance. In proportion as elevation was thus gradually obtained for the smaller end, the space below was filled with rammed earth, and the same process was repeated with the parallel balks of timber, handspikes, and chocks; the small end gradually rising at each successive step, the wall behind increasing in height, and an inclined plane of solid earth gradually increasing its angle with the horizon, until it equalled that at which solid earth could with safety be employed, when the force required being proportionally diminished, timber alone was employed for its elevation. Finally, a scaffolding of timber was erected, embracing three sides of the pedestal, and nearly equal to the ultimate height of the obelisk; ropes were applied to the summit of the shaft, in such directions as to steady and check it; handspikes gave the requisite impetus, until it felt the power of the ropes, and was ultimately and safely lodged in its shallow receptacle." The pedestal consists of a single stone nine feet in height, and seven feet in width. The base of the shaft was six feet in diameter, and an excavation of the same diameter, and about three inches deep, was made in the summit of the pedestal for the reception of the base.

Feb. 18. 1822. At this meeting Dr Dewar read his report on a paper by Dr Dyce of Aberdeen, communicated on the 7th of January, and which contained an account of a singular case of uterine irritation, and its effect upon the mind. The patient was a female servant in a respectable family, and the first symptom of the complaint was a propensity to fall asleep in the evenings. This was followed by the habit of talking in her sleep, on which occasions she not only uttered wild incoherent expressions, but repeated the occurrences of the day, and sung musical airs, both sacred and profane. One evening having fallen asleep in this manner, she imagined herself an episcopal clergyman, went through the ceremony of baptizing three children, and gave an appropriate extempore prayer. Another evening, she, in her sleep, fancied herself living with her aunt at Epsom, and going to the races; placed herself on one of the kitchen stools, and rode upon it into the room, with much noise, and without being awakened: but being severely reprimanded for this grotesque exhibition, she continued free from the habit for a week. The disease soon increased, and came on at different times in the evening and morning. In this state she sometimes dressed herself and the children committed to her care, and answered questions put to her; but the answers were often, though not always, incongruous. One day, when the fit had come on, her fellow-servant was desired to get the key of a closet from her, in order to do the duty of the breakfast table; the girl, however, refused to give up the key, and put down the breakfast herself, with perfect correctness, but with her eyes shut. The access of this affection appeared at irregular intervals, and the patient was generally restored to her senses by being taken out to the cold air, especially when the wind blew in her face. The circumstances which occurred during the paroxysm were

completely forgotten when the paroxysm was over, but generally present to the mind during subsequent paroxysms; for example, when in this state, on after occasions, she told her mistress what was said to her on the evening on which she imagined herself baptizing the three children; and it was remarked, that while under the paroxysm, she knew a person better by looking at the shadow than at the body; that is, she perceived those objects best which were presented merely in outline, or very dimly illuminated.

Dr Dyce describes the symptoms very minutely from the period at which he was called upon for medical advice. It is unnecessary, however, to enter into the very circumstantial detail which he has given. It appears generally, that, while under the paroxysm, her mental faculties were more advantageously exhibited than in the healthy state; that she could sing incomparably better than when in the natural use of her senses; repeat portions of Scripture which she did not appear to have, at any period, deliberately committed to memory; and perform various intellectual operations with truly wonderful accuracy and precision. In the progress of the complaint, she began to recognise persons and surrounding objects, but invariably forgot every thing the instant the fit went off; though, in the succeeding paroxysm, the whole was again distinctly present to her mind. She continued subject at intervals to these paroxysms for more than three months; and at the time when Dr Dyce's account closes, she had, for upwards of a year, been in perfect health, and entirely free from any of these mental wanderings.

This case certainly gives an interesting illustration of the obliquities to which the physiology of the nerves, and the exercise of the mental powers are subject. It is a case of mental disease, attended with some advantageous ma

nifestations of the intellectual powers; and these manifestations disappearing in the same individual in the healthy state. It is an instance of a phenomenon, which is sometimes called double consciousness, but it is more properly a divided consciousness, or double personality, exhibiting, in some measure, two separate and independent trains of thought, and two independent mental capabilities in the same individual; each train of thought, and each capability, being wholly dissevered from the other, and the two states in which they respectively predominate subject to frequent interchanges and alternations. It is therefore totally different from the ordinary cases of somnambulism. It would seem that many things are impressed on the mind, of which, in its ordinary state, it possesses no consciousness, but which present themselves to its view, and become new subjects of thought and consciousness, when it is brought into a new state by the diseased action of the nervous system. Nay, it is even probable, that no idea which has been once present to the mind can ever be absolutely obliterated, but that, on the contrary, it may be called up, of new, by any extraordinary occurrence, as has been observed by persons in the act of drowning, upon whose minds a thousand things have instantaneously flashed, of which they had no previous consciousness. The strong contrast between these opposite mental states was exhibited in a simple girl in the neighbourhood of Stirling, who, in her sleep, talked like a profound philosopher, solved geographical problems, and enlarged on the principles of astronomy, detailing the workings of ideas which had been suggested to her mind by overhearing the lessons which had been given by a tutor to the family in which she lived. Some interesting consequences might be deduced from the explanations we have here attempted, and which this last case seems to confirm ;

but this is not the place to indulge in such speculations.

April 6. A paper by Dr Brewster was read, entitled, "Description of a Monochromatic Lamp, with Observations on the Composition of different Flames, as modified by Reflection, Refraction, and Combustion." The chief object of this paper was to describe the principles and construction of a Monochromatic Lamp for illuminating objects with a homogeneous flame, which the author succeeded in constructing after many unsuccessful attempts. By illuminating microscopic objects with this lamp, a distinctness and perfection of vision was obtained, which extends widely the power of the microscope, and enables it to detect delicate structures, and minute organizations, which are beyond the reach of observation when common light is employed. The author pointed out the application of this lamp to various purposes, both practical and scientific, and particularly to the measurement of minute optical phenomena, such as those of refractive powers, double refraction, and polarization, and the phenomena of periodical colours. As the yellow light discharged from this lamp has an invariable character, the measures of these and other phenomena, taken in such a light by different philosophers, may now be referred to as an unchangeable standard; and they will also have the advantage of being made in the most luminous rays of the spectrum, and of being referable to rays that have nearly a mean refrangibility. The author likewise pointed out the manner in which the prismatic spectrum is attacked and finally extinguished, by the action of differently-coloured absorbing media; and he has established, in opposition to the deductions of Dr Wollaston and Dr Young, that the yellow light has a separate and independent existence in the solar spectrum.

The same evening, a paper by Cap

tain Scoresby junior was read, entitled, "Observations on the Errors of SeaRates of Chronometers, arising from the Magnetism of their Balances; with suggestions for removing this source of error." In this paper Mr Scoresby suggests three means of lessening or obviating altogether the anomalous action of the magnetism of the balance: 1. To employ a substance in the construction of the balance without magnetical properties: 2. To free the balance of any magnetism accidentally acquired: 3. To prevent the unequal action of the magnetic influence, by giving to the chronometer a fixed position, as regards the magnetic meridian. In order to apply the first method, he proposes that the balance be made of platinum. In order to accomplish the second object, he suggests that the flat surface of the balance be ground and polished in the plane of the magnetic equator. To effect the third object, he makes the chronometer traverse upon the plate of a compass-needle; a contrivance which is quite practicable, the magnetic which directs the plate being at such a distance as not to affect the chronometer.

June 17. A paper by the Reverend -Dr Fleming of Flisk was read, entitled, "On a Submarine Forest in the Frith of Tay, with Observations on the Formation of Submarine Forests in general." This remarkable geological phenomenon is similar to the one observed on the coast of Lincolnshire, and described by Dr Joseph Correa de Serra in the Philosophical Transactions for 1799. It occurs on the south bank of the Frith of Tay, and has been observed in detached portions on each side of Flisk beach, to the extent of nearly three miles. After explaining the general and particular appearance of this submarine forest, Dr Fleming proposes a very ingenious and rational explanation of the way in which it has been formed, and he considers his explanation as equally applicable to the subma

rine forest of Mount Bay, Lincolnshire, and that on the west coast of Orkney, described by Mr Watt of Skail, in the Edinburgh Philosophical Journal, iii. 101. The explanation is this: Suppose a lake situated near the sea-shore, having its outlet elevated a few feet above the rise of the tide, and that, by means of mud carried in by the rivulets, and the growth of aquatic plants, this lake has become a marsh, and a stratum of vegetable matter has been formed on the surface of sufficient density to support trees: Suppose a marsh in this condition to have its seaward barrier removed, what consequences would follow? The extremities of the strata, now exposed to the sea, would at every ebb-tide be left dry to a depth equal to the fall of the tide. Much water, formerly prevented from escaping by the altitude of the outlet, would now ooze out from the moist beds, and the subsiding force would act more powerfully in the absence of the water, which previously filled every pore. All the strata above low-water mark would thus collapse, and the surface of the marsh, instead of remaining at its original height, would sink below the level of the sea; but the escape of the water from the strata would not, in such circumstances, be confined to the beds situate above the low water-line. Even those occupying a position considerably lower would be influenced by the change; for even in such the water would be squeezed out, in consequence of the pressure of all the matter of the strata above the low-water mark, exerted during every ebb, in the expulsion of the water at the lowest level, thus permitting the subsidence of the strata to take place even to the lowest beds of the morass. It is in consequence of this drainage that the depression of the surface of a marsh many feet below its original level is conceived by the author to take place, and that, to use his

The first paper which possesses any general interest was an Analysis of the Meteoric Stone of Juvenas, read to the academy on the 29th of January. The author is M. Laugier, to whom we are indebted for a very accurate account of the remarkable aerolite which fell at Jonzac on the 13th of June 1819, and which differed from all those formerly analysed in being entirely without nickel, and in containing only a very small quantity of sulphur and magnesia, with a proportionally large quantity of lime and alumina. The results of M. Laugier's analysis of the meteoric stone which fell at Juvenas, in the department of the Ardeche, on the 15th of June 1821, are in perfect accordance with those which he obtained from the aerolite of Jonzac. The entire mass weighed 112 kilogrammes, (about 258 pounds avoirdupois,) and its fall was, accompanied with the phenomena generally observed in similar circumstances. Like other meteoric stones it was easily

pulverised, no globule of iron offering resistance to the pestle, but it exhibited small crystals of a sensible cleavage, which M. Laugier considers as a species of feldspath. It was but partially acted upon by the acids, and the solutions contained only portions of iron, alumina, and lime; the greater part of the substance remaining totally unaffected. They exhibited no trace of silica or chromium, and but a small quantity of sulphuric acid, proceeding from the sulphur of the stone when nitric acid was employed: when the hydro-chloric acid was used, the sulphur was disengaged with the hydrogen. The analysis by potash was found much more easy and accurate. On the application of heat, the substance assumed a yellow colour, which, when the fusion was complete, changed to a deep green, caused, no doubt, by the manganese which formed a part of it. This solution, heated to ebullition, deposited the manganese and potash by which the green colour was produced, and retained only the yellow colour occasioned by the chromium of the stone, and when supersaturated by the nitric acid, gave, by means of the solution of the proto-nitrate of mercury, a yellow orange-coloured precipitate, which, after calcination, yielded the green oxide of chromium. The portion of the mass not changed with potash is easily dissolved without residuum in the hydrochloric acid, to which it communicates a yellow-orange colour; and on evaporating the solution, all the silica of the stone, which had not been dissolved with the chromium in the potash, is obtained. The alumina is precipitated from the potash by the solution of the hydro-chlorate of ammonia. The iron obtained is not pure, but is separated from the oxide of manganese by redissolving it in the hydro-chloric acid, mixed with succinate of ammonia. The ammoniacal solution, when freed from the oxides of iron, manganese, and alu