The cavern St. George's is situated in a wood of pines, thinly scattered. There are two entrances to it, at about the distance of twelve feet from each other. The length of its icy surface is seventy-five feet, and the mean width forty feet. In ordinary years it furnishes ice only to a small number of families, but when the winter is such as not to afford enough for the ice-houses of Geneva, recourse is had to it. The working of the ice is the same as that of a quarry. It is cut with appropriate tools into long wedges, and divided by transverse sections, about a foot from each other, and sufficiently deep to enable the workmen to detach blocks of the size of a cubic foot. The extent of the workable surface is 3000 square feet, from which there is carried off every second day, during the summer, about twenty-five quintals, or, in all, about 195,000 lb. At the extremity of this cave, at a certain height against its partitions, there are icy stalactites resembling those of carbonate of lime, formed by the filtration of a small stream of water, which is constantly freezing. The thermometer, at the entrance, stood at 60° Fahrenheit, and, in the middle, at two feet above the floor, at 3410. The cold is so great, that when two blocks of ice are left close to each other on the bottom of the cave, they are, in the course of a few hours, frozen together. The cavern of Mont Brezon is not so large as those already described, being only about thirty-five feet in length, twenty-five in breadth, and ten or twelve in height. The temperature of the interior was 41°. It is impossible to estimate the quantity of ice in it, it is so irregular; part of it seemed to be a remnant of the snow of the preceding year, the remainder was produced by the congelation of the water.

The cave of Mount Vergy is of

feet long, and thirty wide. Its tem perature was 340 Fahrenheit, while that of the atmosphere was 58°. The guide who accompanied Pictet, informed him that the last time he visited it there was no ice, and that it is found only when the temperature, of the atmosphere is high, the quantity increasing according as the temperature rises.

Another of these remarkable caves has lately been described by M. Dufour, Lieutenant-Colonel of engineers. It exists in the side of a rugged mountain called Rothorn, near Thun, the ascent of which is very steep. The rock is calcareous, and of a deep gray colour, mixed with beds of clay, of from 8 to 12 inches in thickness. The strata are cut by fissures perpendicular to them, and to the general plane of the slope, so that they present externally the appearance of a wall of rouble work. The peaks of the mountains are crowned by a sandstone containing a great many particles of quartz. The ice-house of Rothorn is about 5840 feet above the level of the sea. It is covered by a mass of rocks of 1000 or 1500 feet in thickness, through the numerous fissures of which water passes and falls, drop by drop, into the cave, by which, owing chiefly to its evaporation, it is so much cooled, that it congeals when it reaches the floor, and thus a constant supply of ice is kept up. The height of the cave is at the entrance 25 feet, but it immediately increases to about 50; its width is about 100, and its general form is that of a Z. The first mass of ice is met with where the external light penetrates only in small quantity; consequently it cannot be formed by the winter's snow, which might be driven in by the wind. A little further in the ice covers the floor of the cave, and is so transparent, that the rocks can be easily seen through it. Beyond this, there is an inclined plane of ice, which leads to a magnificent hall, from the sides of which are suspended large masses or stalagmites of ice, the surface of which seems to be constantly undergoing evaporation. Though the heat of the external air was considerable, a thermometer at different places in the grotto never rose above 38°. The extremity of this cavern is called Shafflock or Sheeps-hole, from its affording an asylum to those animals, from the burning heat of the sun, and when surprised by a storm.

In attempting to account for the formation of ice in these caves, Pictet states, that we must have recourse to some local cause, as it does not depend on the winter's snow, or "the temperature of the earth; for in those latitudes the mean heat is far above the freezing point. It was remarked that there always issued a stream of cold air from the different openings connected with them, which, constantly exciting evaporation from the surface of the water, must produce a great degree of cold. This is supported by numerous facts. Thus there are many caves so formed, as to allow a continual flow of air through them, and which is many degrees colder at its exit than at its entrance. In one near Rome, the air as it entered was at 78°, but, as it issued, it was as low as 44°. The same is the case in many instances, there being a difference of from 15° to 20°, or even 30°, in the temperature of the air; and in all of them, the hotter the summer, the greater is the strength of the current. This is occasioned by the difference in the weight of the external and internal air, the heaviest rushing out, and having its place supplied by a current lighter and warmer, which, by accelerating evaporation, is itself cooled, and produces a great degree of cold in the cave-in those just described, perhaps sufficient to cause the water to freeze; for it is well known that water may be frozen by the cold excited merely by its evaporation.

HISTORY AND DISTRIBUTION OF THE

PARROT.

The Greeks seem at first to have known only one species of parrot, imported from the East by one of the captains of Alexander's fleet. Aristotle speaks of it as a rare bird. Their beauty and faculty of speech soon made them objects of high request among the luxurious Romans, whom Cato reproached for this puerile attachment. In his time, they kept them in cages of silver and ivory, and paid as much for them as for a slave. Till the time of Nero

they knew no other species, when they were discovered by them in an island, far up the Nile, called Gaganda. The Portuguese, who first doubled the Cape of Good Hope, found the whole coast of Africa, and the islands of the Indian ocean, peopled with various tribes of them, and in such numbers, that they with difficulty preserved the rice and maize from them. They were, however, far inferior to those found in the new world, some of the islands of which are called Parrot Islands, from the immense quantity of parrots that frequented them. The green paroquet, with a red neck, is the first of this genus that was brought into Europe, and it is now known only by the description given of it by the ancients. The birds of this class have been arranged in two great divisionsthose of the old and those of the new world; to the former belong cockatoos, parrots, lories, and paroquets; to the latter, acas, or maccaws, amazons, criks, popinjays, and paroquets. The lories inhabit the Moluccas, New Guinea, and other Asiatic islands. Owing to their powerless flight, the inhabitants of one island are quite different from those of the adjacent one. The touis or short tailed parrakeets, are the smallest of all the American parrots. They are of the size of a sparrow, and are, in general, incapable of speech.

Buffon supposed that parrots were confined to within twenty-five degrees on each side of the Equator; but in this he is incorrect. A species called the Carolina parrot inhabits Guiana, and migrates into Virginia and Carolina. Another species, the Illinois parrot, goes from South America far northward, being common on the banks of the Ohio and the southern shores of lake Erie. A third species, the emerald parrot, exists in the neighbourhood of the Straits of Magellan, and various others occur in different quarters. Of this splendid genus there are no less than 239 species.

ACTION OF HEAT AND COMPRESSION

ON FLUIDS.

It is well known that, by means of a Papin's digester, fluids may have their temperature raised far above their boiling point, but at the same time, they are subjected to a very great pressure from the vapour generated, which it is supposed would prove a bar to their complete conversion into the aeriform state. In reflecting on this subject, it occurred to M. de la Tour, that the expansion of a volatile fluid had necessarily some limit, beyond which, notwithstanding the pressure, it would be converted into vapour. To ascertain whether this was the case, he put some alcohol into a small glass tube, so as to occupy nearly two-fifths of it, and sealed it hermetically by a blowpipe. The tube was then cautiously heated, and in proportion as the fluid expanded, its mobility became greater; and after attaining nearly double its volume, it suddenly disappeared, and the tube became filled with a transparent vapour, which, on cooling, formed a thick cloud, and the fluid assumed its original state. A second tube, nearly half full, gave the same result; but one, more than half full, broke on the application of heat. Similar experiments were made with oil of petroleum of specific gravity 807, and with ether, which presented similar results, excepting that the latter required less space than the former to be converted into vapour without breaking the tube, and the petroleum less than alcohol, seeming to indicate that the more a fluid is naturally dilated, the less volume it requires to attain its maximum of expansion. In the above-mentioned experiments, the tubes were exhausted of their air before they were sealed, but it was found that the same occurred though it was left in; the progressive expansion of the fluid was even more easily estimated, as there was no inconvenient ebullition. The last experiment was made with a tube one-third filled with water; the glass lost its transparency, but broke in a few seconds afterwards. By putting a little carbonate of soda along with the fluid, its action on the glass was in a great measure prevented, and the effects of heat and compression on it were observed. It was found that at the temperature of about melting zinc it passed into vapour in a space nearly four times that of its original volume; whereas alcohol, petroleum, and ether, undergo the same change in a volume rather exceeding twice that of the fluid. The pressure exerted during

the change of form, De la Tour found varied in the different fluids subjected to experiment. By exposing them to heat in a particular apparatus, he ascertained that alcohol may be reduced to vapour in a space rather less than three times its bulk, and that it then exerts a pressure equiva-. lent to that of 119 atmospheres, while the pressure of ether, converted into vapour, is only 37 atmospheres; the former requiring a temperature of 392 F. the latter of 492. These experiments promise to lead to interest ing results, as it is likely that, by the joint action of heat and pressure, substances may be made to combine which cannot otherwise be united, and thus their action on each other may be ascertained.

FLUID IN THE CAVITIES OF CRYSTALS.

A fluid of a very singular nature, has been discovered by Dr. Brewster in the cavities of minerals. It possesses the remarkable property of expanding thirty times more than water, and by a heat from 75 to 83 it enlarges, so as to occupy the cavity which contained it, and resumes its original state as the temperature falls. It is remarkable for its optical properties and for its extreme volubility, adhering very slightly to the sides of the crystal. It is almost always accompanied by another fluid like water, with which it does not mix, and which does not perceptibly expand at the above-mentioned temperature. In a specimen of chrysoberil, Dr. Brewster has discovered a stratum of these cavities in which he has reckoned thirty thousand in the space of one-seventh of an inch square, each containing this new fluid, a portion of the liquid like water, and a vacuity, all of which vacuities disappear at the temperature of 83, being then filled by the expanded fluid. VARIATION IN THE BULBS OF THER

MOMETERS.

Mr. Flauguergues has observed, that in mercurial thermometers, in which there is a vacuum above the mercury, the freezing point has gradually risen nine-tenths of a degree, and has gone on increasing for years, which is attributed to a change of form occasioned on the bulb by the pressure of the air; he therefore recommends that their stems should be left open, so that the pressure on the outside and inside may be the same.

The same fact has been long ago noticed by Bellani, of Milan, who mentions the following experiment to prove that the bulbs of thermometers are liable to alter their form. Take a mercury thermometer graduated above the boiling point, and the degrees of which are so large that the tenth of a degree can be easily seen, plunge it into boiling water and then into melting snow, and it will be found that the freezing point has sunk onetenth of a degree in consequence of the expanded glass not having resumed its original form.

PROCEEDINGS OF THE ROYAL

SOCIETY.

February 27.-Mr. Goldenham read a paper on the velocity and force of sound, the experiments on which were made at Madras. At the fort, a gun is fired in the morning at daylight, and in the evening at eight o'clock; and at the artillery cantonments another is fired at sunrise and sunset; the former of which is very nearly double the distance of the other from the observatory, affording, therefore, a good opportunity of ascertaining whether sound travels at the same rate through paths of different lengths. The observations were made with Arnold's chronometers, making 100 beats in 40 seconds; the movements of which were counted by two people, from the instant the flash of the gun was seen, till the report was heard. The heights of the barometer, thermometer, and hygrometer, the direction of the wind, and the general state of the weather, were at the same time noticed. From the experiments thus made, it appears that the mean velocity of sound, by the observations on the fort gun, is 11421 feet per second, and by those on the artillery gun 1142%; the mean of both is 1142, which is very nearly that previously assigned by Newton and Halley. Mr. Goldenham has likewise shown, that the velocity of sound is considerably affected by the state of the atmosphere and by the wind, contrary to what has been asserted by others. The velocity, he found, increases to a maximum at the middle of the year, being then 1164 feet per second, the minimum is 1099 feet.

merous experiments have been al ready made on this subject by Mr. John Hunter, Dr. Gordon, and Dr. Davy, which disagree in their results, occasioned, according to Dr. Scudamore, by the difference in the temperature of different parts of the same portion of blood. From his experiments he concludes that there is slight ght evolution of heat during coagulation. It commences when the fibrin begins to concrete, but continues till the whole of the fluid is coagulated.

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March 13-On Fluid Chlorine, by Mr. Faraday. When chlorine (oximuriatic acid gas) is exposed to cold, crystals are formed on the sides of the vessel, which were at one time supposed to be pure chlorine, but which Sir H. Davy proved were a compound of it and water. It occurred to Sir H. Davy, that some interesting results might be obtained by decomposing this substance under pressure; and he requested Mr. Faraday to make experiments on the subject. With this view some of the crystals, dried on bibulous paper, were put into a glass tube, which was then hermetically sealed by a blowpipe. When plunged into water, at the temperature of 100°, two fluids were produced, one of a pale yellow, the other of a deep green colour, and above these there was an atmosphere of chlorine much darker than usual. On opening the tube an explosion took place, the yellow fluid disappeared, and chlorine was evolved. This yellow fluid Mr. Faraday has found to be liquid chlorine. It may be distilled from the other, along with which it is produced in the tube by the application of a gentle heat. It is then limpid, and remaius fluid at zero. It is very volatile, rising in vapour when exposed to the air. Since the above paper was read to the society, we understand that Mr. Faraday has succeeded in rendering fluid euchlorine, nitrous oxid, sulphurous acid, carbonic acid, and cyanogen gases. All the liquids obtained from them are highly volatile, and, with the exception of that from euchlorine, are colourless.

equal to ten horses; its generator (in place of a boiler) holds about eight gallons; the working cylinder is only eighteen inches long. The parts have been proved, by hydraulic pressure, to bear a force equal to two thousand pounds on the square inch; but a weak part has been subsequently introduced into it, which shall give way at one thousand pounds of pressure, the engine being intended to be worked by steam raised to seven hundred pounds.

REMARKABLE COLD IN INVERNESSSHIRE.

A very extraordinary degree of cold was observed at Doune, in Inverness-shire, on the 6th of February. The following are the observations, made with the thermometer:-

M. Fresnel has ascribed the ascent of clouds in the atmosphere to the following cause. Air and all colourless aeriform bodies allow the solar rays, and even radiant heat, to pass through them without sensibly heating them. When a cloud, therefore, is composed of small globules of water, or minute crystals of snow, the air in the interior of the cloud becomes heated from the contact of the matter with which it is surrounded; it will, therefore, dilate, and the cloud will rise in the atmosphere to a height depending on the fineness of its particles, and the intervals which separate them. The fact that vapour exists in a vesicular form is well known, and that clouds are composed of it in this state, is generally be lieved; but it is by no means established, that the vesicles are filled withair; this opinion of Fresnel must,

therefore, be received with caution, more particularly as the suspension of clouds is ascribed by M. Gay Lussac to a very different cause. He supposes that they are pushed upwards by ascending currents in the atmosphere, occasioned by the heat flying off from the surface of the globe, and that they continue to rise till this force of impulsion is balanced by the weight of the cloud. In proof of this opinion, he states that a soapbubble will not rise in a room, but will fall directly when left to its own weight; but if it be blown in the open air above a heated soil, it will ascend to a certain height, being wafted up by the currents of heated air.

SKULLS FOUND IN GERMANY.

There has been lately found in the neighbourhood of Halberstadt, in Saxony, a number of skulls, which, it is said, present marked differences from the European race, and which approach the Coptic form. Their most remarkable feature is, their having only grinding teeth, the incisors being wanting, from which it is conjectured that they belonged to a frugiferous race, perhaps of the primitive or antediluvian world. Such, is the account given of these skulls; M. Blainville, however, makes the following remarks on them: with-regard to the absence of incisors, if the fact be certain, it is more than probable that it is merely accidental. He thinks it more rational to suppose that it is analogous to the peculiar disposition of the canine and incisor. teeth, which seem wanting in the skulls of Egyptian mummies, but which have only been worn down, as has been observed by Soemmering; and as Blainville has himself found in those from Cairo, presented to him by M. Tedenat, son of the French Consul. The skulls of these mummies seem smaller than the generality of those of Europeans, especially about the forehead; the eyes are large, or rather the margins of the eyelids are much extended. The profile is not that of the negro, though it resembles it about the lower part of the face. The incisors are much worn, and cut square, as are also the canine teeth.

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