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certain height. According to the experiments of Pictet, to whom we owe the discovery of this anomaly, a thermometer then suspended in the air at two yards from the ground may indicate throughout the night from 31° to 51° Fahr. less than a thermometer similarly suspended in the air, but fifteen or sixteen yards higher.
If it be recollected that solid bodies placed on the surface of the ground, pass by means of radiation under a clear sky, to a temperature much below that of the surrounding air, it will not be denied that this air must at length be affected, by means of contact, with the same coldness, and in a greater degree, according as it is nearer the earth. In this, therefore, we find a plausible explanation of the curious fact made known by the natural philosopher of Geneva. Our navigators will impart to it the character of a demonstration, if they repeat Pictet's experiment in the open sea, by comparing, during a clear and tranquil night, a thermometer placed on the deck with another attached to the mast-head. Not that the superficial stratum of the ocean does not experience the same effects of nocturnal radiation, in the same manner as down, wool, grass, &c.; but after its temperature has diminished, this bed of stratum is precipitated, because its specific density has become greater than that of the inferior liquid beds. We are not, therefore, to expect in this case, the enormous local colds observed by Wells in certain bodies placed on the surface of the earth, nor the anomalous coldness of the inferior air, which seems to be the consequence of them. Everything, indeed, leads to the belief, that the increasing progression of atmospheric temperature noticed on land, does not exist in the open sea; and that there the thermometer on the deck, and that at the summit of the mast, will indicate very nearly the same degree. The experiment, nevertheless, is not the less deserving of attention. In the estimation of a prudent natural philosopher, there is always an immense distance between the result of a conjecture and that of an observation.
EXPEDITIOUS METHOD OF DETERMINING MEAN TEMPERATURES IN EQUINOCTIAL COUNTRIES.—In our climates, the stratum of the earth which undergoes neither diurnal nor annual variations of temperature, is situated at a great distance from the surface of the ground. But such is not the case in equinoctial regions; for, according to the observations of M. Boussingault, nothing more is necessary than merely to sink a thermometer to the depth of about one foot English, in order to make it indicate constantly the same degree, or very nearly so. Travellers, therefore, may determine very exactly the mean temperature of all the places they visit between the tropics, either in plains or in mountains, by having the precaution to furnish themselves with a miner's piercer, with which it is easy, in a few minutes, to pierce a hole in the ground of the required depth. It will be found that the action of this instrument on rocks and on the soil, occasions a developement of heat, and the observer should always wait till that be entirely dissipated before he commence his experiments. It is likewise necessary that the air in the hole should not be renewed during the whole time of their continuance. A soft substance, such as pasteboard, covered with a large stone, will form a sufficient preventive. The thermometer ought to have a string attached to it, by means of which it may again be
The observations of M. Boussingault, of which we have availed ourselves, in order to recommend perforations to the trifling depth of a foot, as conducting very expeditiously to the determination of mean temperatures in all intertropical countries, have been made in sheltered places, in the ground, under Indian huts, and under mere sheds. In these situations, the soil was sheltered from the direct warmth produced by absorption of the solar light, from nocturnal radiation, and infiltration of rains. Every one trying the experiment should place himself in similar circumstances, for there can be no doubt that in the open air, and in places remote from shelter, it would be necessary to penetrate to a much greater depth in the ground, in order to reach the bed possessing an equal temperature.
It is well known that the temperature of the water in wells of moderate depth, also affords an easy and exact mode of ascertaining the mean temperature of the surface. This method, therefore, must not be omitted among those recommended by the Academy.
OBSERVATIONS TO BE MADE ON THERMAL Springs.-If it be the case, as everything leads us to believe, that the high temperatures of the springs called thermal, are solely the consequences of the depth from which they rise, it is natural to suppose that the warmest springs should be the least numerous. At the same time, is it not extraordinary, that none have hitherto been observed whose temperature has approached the boiling point within 36° Fahr. * ? If we are not deceived by some vague reports, the Philippine Islands, that of Luçon in particular, are likely to afford the means of elucidating this subject. There especially, as in many other places where thermal springs exist, the most interesting data that can be collected, are such as tend to prove that the temperature of a very abundant spring varies, or does not vary, with the lapse of ages; and in particular local observations, with a view to show the necessity of the fluid having a passage across the very deep-lying strata of the earth.
* We do not include in this category of thermal springs the Geysers of Iceland, and other analogous phenomeaa, which evidently depend on volcanoes at present in a state of activity. The warmest thermal spring, properly so called, with which we are acquainted, Chaudes Aigues in Auvergne, is 176° Fahrenheit. Since this article was written for the expedition of La Bonite, MM. von Humboldt and Boussingault have given me, as the temperature of the spring Las Trincheras (Venezuela) in 1800, 195° Fahr., and in 1823, 206° Fahr. This spring, according to them, has no direct connexion with any active volcano. On the other hand, the Duke of Ragusa writes me, that, at Broussa, at the foot of the Mount Olympus, he found the thermal bath, called by the Turks Chirurchiest, to be 183°•2 Fahr. it seems, therefore, that 1766 Fahr. is the maximum temperature of European springs only.
[To be continued. ]
Precision in Scientific Terms. No. II. HORIZONTAL-LEVEL.—“In common language, the term level is the same as horizontal; and this may be taken as its true meaning when a small extent of surface is spoken of; but it will be seen to have a very different meaning when applied to the surfaces of fluids of great extent, as the sea, or large lakes.
The earth's figure may be considered as spherical, for the slight deviation from this form may be disregarded in the present inquiry. Now the inequalities on the surface of the terrestrial part of the earth, insignificant though they be when compared with the whole mass of the earth, do not exist at all on the surface of still water, as on the surface of a calm sea. But it is known by observation that the surface of the sea is uniformly curved, and would, if continued uninterruptedly in every direction, present a spherical surface. This is the observed fact, and the same conclusion may be arrived at in the following
Gravity, at the earth's surface is a uniform force, and acts in a direction perpendicular to that surface; that is, in the direction of the plumb-line. It acts equally on all bodies at equal distances from the centre of the earth, and unequally on bodies at different distances, exerting a greater action on those at a less distance than on those at a greater. Hence, if the surface of still water have all its points at the same distance from the centre of the earth, every particle at its surface is equally acted on by gravity. But if any two points on its surface be at different distances from the centre, the particles at the points will be acted on unequally; and the pressure at different points of the surface being unequal, the fluid will not be at rest. Hence it is evident, that under the action of a force, such as gravity is known to be, a fluid mass must settle down into a spherical form, and the fluid will not be at rest until it is in this form; and this agrees with what was stated above, as the observed fact.
This spherical surface is called a level surface; and if the whole globe were covered with water, there would have been but one surface, and therefore but one level. But the fact is, tliat there are many different surfaces; and though theory shows they all ought to be, and observation shows that they all are, spherical surfaces, yet they are not concentric*, but are at very different distances from the centre.
This is expressed by saying that they are all level surfaces, but not all on the same level; and one level is said to be above or below another level, according as it is at a greater or less distance from the centre of the earth."—Webster, Principles of Hydrostatics. 1835.
Ashmolean Society-(Feb. 1836.)
February last :
* This cannot be true, it is clear from the previous reasoning that they can have but one common centre, -that of the earth ; and, therefore, must be concentric. The author, by an inconceivable inadvertency for so accomplished a teacher, seems to have confounded concentric with equidistant.--Ed.
Prize Subjects, 1836. Institute of British Architects, London. Medals are offered by the Institute of British Architects, for Essays on the following subjects:
1. On the Practical Application of the Theory of Sound in the Construction of Edifices, by which the Rules may be ascertained for building Theatres, Churches, H and other places for Public Meetings, in the manner most favourable for the transmission of Sound."
2. “On the Effect which would result to Architecture, in regard to Design and Arrangement, from the general Introduction of Iron in the Construction of Buildings."
The Essays are to be delivered to the Institute ‘on or before the noon of December 31st, of the present year. The Conditions, &c., may be obtained from the honorary secretaries at 43, King Street, Covent Garden.
New mode of preserving Animal Substances. “The author of this discovery, Sig. Girolamo Segato, is already favourably known to the scientific world, as the author and engraver of improved maps of Africa and Morocc). Ardent in the pursuit of science, he traversed the deserts of Northern Africa, and by his researches, corrected and considerably advanced the knowledge of those regions. It was while travelling in these parts that he received the first hint of this great discovery. In the path of one of those interesting phenomena of the African deserts—a vortex of sand,which his curiosity prompted him to trace, he, one day, discovered a carbonized substance, that upon closer investigation proved to have been originally animal matter, and to have been carbonized by the scorching heat of the sand. He afterwards discovered an entire human carcass, partly black, partly of a sooty hue, about a third less than the ordinary size of man, and ail perfectly carbonized. It occurred to him that this accidental process of nature might be imitated by art to the perfect preservation of animal substances. To discover how occupied now his whole attention. At the end of some months devoted to this pursuit, the happy thought flashed upon his mind, which was to lead him to the discovery of the desired secret. Compelled to return to Italy by a dangerous malady, brought on by nearly a week's exposure to an unwholesome atmosphere in a pyramid of Abu-Sir, which he had entered for the purpose of extending his scientific researches, he was obliged to intermit for a time his favourite pursuit, but, after regaining his health, he again gave himself to it with renewed ardour; and, after a short time, succeeded to the highest degree of his most sanguine expectations.
The following are some of the results obtained by the discovery. Entire animal bodies yield as readily to the process as small portions. They become hard, taking a consistence entirely stony. The skin, muscles, nerves, veins, blood, &c., all undergo this wonderful change; and to effect this, it is not necessary to remove any part of the viscera. The colour, forms, and general characters of the parts remain the same. Offensive substances lose their smell. Putrefaction is checked at once. What is most wonderful of all is, that if the process be carried only to a given degree, the joints remain perfectly flexible. Skeletons eren remain united by their own natural ligaments, which become solid although they retain their pliancy. Moisture and insects never injure them. Their volume diminishes a little; their weight remains almost the same. Hair continues firm in its place, and retains its natural appearance. Birds and fishes lose neither their feathers, membranes, scales, nor colours. The
insect preserves its minutest appendage. The eyes in most animals sparkle as in life, and from their want of motion alone would you suppose vitality extinct.
The following are some of the objects that have been subjected to the petrifying process, and are now exhibited in the studio of Sig. Segato. One of the first of his experiments was performed upon a canary-bird (Fringilla canaria, Lin. It is still preserved unaltered, although it is now ten years since the experiment was performed ; and it has been submitted to the action of water and of insects. A parrot (Psittacus æstivus, Lin.) retains its original brilliancy of plumage unimpaired. Eggs of the land-turtle, turtles, various tarantulæ, a water-snake, a toad, various kinds of fish, snails, and insects, are in a perfect state of preservation. To these are added various parts of the human body. A hand of a lady, who died of consumption, preserves the emaciation of the disease and of death. Another of a man is flexible in the different phalangic articulations, and yet unalterable; a foot with the nails perfectly. fast; a collection of all the intestines of a child, in their natural colours and forms, with the fecal matters unremoved; the liver of a man who died from intemperance, dark and lustrous like ebony; an entire human brain with its convolutions, of extreme hardness; the skin of a woman's breast naturally configured ; a pate of a girl, perfectly flexible, from which the hair hangs in curls; the head of an infant, partly destroyed and discoloured by putrefaction. There is also in the cabinet of Sig. Segato, a table constructed as follows: a spheroidal surface of wood contains a parallelogram, composed of 214 pieces, regularly arranged. These to the eye appear like the most beautiful pietre dure that have been produced by nature. Their various colours, polish, and splendour, and their surprising hardness, would leave no doubt of their stony character. The sharpest file, with difficulty, makes an impression on any of them, some it does not attack at all. These pieces are all portions of the human body, hardened by this new process; as the heart, liver, pancreas, spleen, tongue, brain, arteries, &c., &c., all resembling the most highly polished precious marbles. An entire body has not yet been tried, principally on account of the limited resources of Sig. Segato, although the expense would be about one-tenth only of that of embalming by the ordinary process.
Great advantages to science, especially to natural history and human anatomy, are expected to result from this discovery; and it is even confidently believed, that the remains of friends, of men of science and of worth, may be preserved for ages in the exact form and appearance in which the hand of death found them, with nothing offensive or repulsive about them.
As vouchers for the accuracy of the statements, the certificates of many of the most distinguished physicians, professors, and men of science in Florence, where Sig. Segato resides, are appended. Among them it is sufficient to mention the names of Sig. Betti, professor of Physiology; Sig. Zannetti, professor of Human Anatomy; and Dr. Gazzeri, professor of Chemistry. Day, From a pamphlet published in Florence in the Summer of 1835.-Silliman's Journal, No. LX., 1836.
Remarkable Sealing-Wax used by the Grand Vizier. During an audience of the British Ambassador, attended by his suite, at the Turkish court, it was observed that “the vizier sent a sealed paper wrapped in muslin, by a messenger, to the sultan. In sealing this letter with red wax, he used no candle, or any other process that I could see, to dissolve it, so as to make it susceptible of an impression, though he impressed a seal upon it."Walsh, Residence at Constantinople. London, 1836.