Cement. The following is a very excellent cement for the use of turners and artisans in general. The receipt is due to Mr. S. Parley : -16 parts of whiting are to be finely powdered and heated to redness to drive off all the water. When cold, it is to be mixed with 16 parts of black resin, and one part of bees-wax; the latter having been previously melted together, and the whole stirred until of an uniform consistence. [Tech. Rep. i. 416. Intensity of the Magnetic Force in different parts of the World. The following table is the result of Professor Hanstein's laborious observations. Places. Diff Intensities. 0° 0' 1.0000 42° 10' 1.3155 Paris, 68° 38' 1.3482 London, 70° 33' 1.4142 Christiana, 72° 30' 1.4959 Arendahl, 72° 45' 1.4756 74° 21' 1.4941 84° 25' 1.6685 [Tach's Correspondence. Large Human Calculus.-A large human calculus has been described by Professor Cumming, of Cambridge: it weighs thirty-two ounces, and measures 154 inches in circumference. Its specific gravity is 1.756. The nucleus is lithic acid, and to this succeeds a considerable portion of the oxalate of lime, then layers of the triple phosphate, covered by a thick coating of lithic acid, the external surface being composed principally of the fusible calculus. It is in the possession of Trinity College. A calculus is also noticed from the intestines of a hare: it is composed of vegetable matter and the phosphates. Captains Hodgson and Herbert have determined the highest of the Himalayas to be 25,589 feet, and the lowest to be 16,043 feet, above the level of the sea ; and that twenty of the peaks are more elevated than Chimborazo, the highest of the Andes. Improved Signal for Trigonometrical Measurements.-A new kind of signal has been used by M. Gauss of Gottingen, in a trigonometrical measurement undertaken in Hanover, which appears to possess many advantages. It consists of reflected solar light: that astronomer having remarked that the light reflected by a small plane mirror, was sufficiently intense to be observed at greater distances than those of the sides of his greatest triangles, had a couple of instruments made which he called Heliotropes, and which, though simpler in their construction than the Heliostat of S'Gravesande, were, like it, intended to reflect the sun's rays in a constant direction. Whilst these instruments were preparing, M. Gauss made use of Hadley's sextant, which, for this purpose, was mounted on a solid foot in the following manner: The plane of the instrument being inclined to the proper degree, the angle between the sun and the terrestrial object to which the sun's rays are to be reflected by the moveable or great mirror of the instrument is to be observed. Then, without altering the apparatus otherwise, the arm which carries the mirror is to be moved, until the index is at double the angle observed, when the sun's rays will be reflected on the spot desired, so that from that point the image of the sun may be seen in the mirror like a star. The same result may be obtained by previously fixing a third mirror above the moveable mirror, on the same arm, and perpendicular like it to the plane of the instrument; but which makes, with the plane of the great mirror, an angle equal to the compliment of 90 degrees of the angle formed by the visual ray with the plane of the third mirror. When, with a sextant thus prepared and fixed on a foot, the distance of the object from the centre of the sun is observed, this third mirror reflects the sun's rays at the same moment on the object itself, and an observer being there, the signal will be the light reflected from the sextant. It is easy, by a little practice, to give that motion to the mirror which is necessary to throw the sun's rays for some time on the same object; for, in consequence of the imperfection of the mirror, the field over which the rays are reflected is large enough to compensate for any little irregularity in the movement. M. Gauss has found that mirrors, two inches by an inch and a quarter, are quite large enough for these purposes: In some experiments, made with a view of estimating the distance to which these signals would be visible, a heliotrope and a sextant were placed two geographical miles from each other, the luminous points reflected by those mirrors could be seen by the naked eye, and when viewed through the telescope of the theodolite were too brilliant to give exact points; but when, in place of the sun's light that from a bright cloud was reflected by them, they gave an excellent mark. At a distance of five miles, the points were still visible, like stars, by the naked eye, and they could be seen through the telescope of the instrument, even in heavy weather, when the great signal itself could not be distinguished. At last the distance was increased to 11 or 12 geographical miles, the stations being at Inselberg and Hohenhagen, and the operators MM. Gauss and Enke. The light was reflected at intervals by the sextant from Inselberg to Hohenhagen, whilst the light was constantly reflected from the latter to the former place the heliotrope; these experiments continued ten days in various circumstances with great success. Each observer reciprocally saw the points at the other station, whilst frequently the mountains on which they were placed could scarcely be seen by the telescope. More than once the light of the heliotrope pierced through mists and even showers of rain. In general the angles observed by these signals were in greater accordance with each other, than when the ordinary signals have been used. Baron de Zach proposes a simplification of the reflecting apparatus. He supposes a polyhedral reflector, similar to those sometimes used by bird-catchers, to rotate on an axis passing through the number of its facets, there will then continually be a facet reflecting the light in the proper direction; and farther, such a signal would be visible in all directions. In a trial of this process made in the small way, a piece a of rock crystal, cut with many facets, was made to rotate rapidly in the sunshine, it was seen distinctly from all situations at the distance of 2,000 toises. [Bib. Univ. xviii. 151. FROM THE PHILOSOPHICAL MAGAZINE, Prizes proposed by the French Royal Academy of Sciences, for 1823. In Physics.-The origin of animal heat is not established in an incontestable manner, and philosophers are still divided in opinion on the subject, notwithstanding its great importance to the progress of physiology. The Academy offers a gold medal of the value of 3000 francs, to be awarded in the public sitting of the year 1823, for the best treatise founded on actual experiments, on the causes, whether chemical or physiological, of animal heat. It is particularly desired to know exactly the degree of heat emitted by a healthy animal in a given time, and the carbonic acid which it produces in respiration ; and what proportions such heat bears to that produced by the combustion of carbon in the formation of the same quantity of carbonic acid. The essays to be transmitted to the secretariat of the Institute before the first of January, 1823. In Mathematics.-The Academy, persuaded that the theory of heat is one of the most interesting objects to which mathematics can be applied, propose the following questions for a prize to be awarded in March, 1824. 1. What is the density, as proved by experiments, which liquids, especially mercury, water, alcohol, and sulphuric ether, acquire by degrees of compression equivalent to the weight of so many atmospheres? 2. How to measure the effects of the heat produced by these compressions ? The prize to be a gold medal of the value of 3000 francs. The essays to be transmitted before the first of January, 1824. Prizes founded by M. Alhumbert.— The late M. Alhumbert having bequeathed an annuity of 300 francs to be employed in promoting the sciences and arts, the king has authorized the Academies of Sciences and Fine Arts to distribute alternately every year a prize of that value. The Academy proposes the following subject for the competition of To compare anatomically the structure of a fish and that of a reptile; the two species to be chosen by the competitors. Prize of Experimental Physiology founded by M. de Montyon.The prize a gold medal of the value of 895 francs, for the work, printed or in MS. which sball appear to have contributed most to the progress of experimental physiology.—To be sent to the secretariat of the institution before the first of January, 1823. Prize in Mechanics founded by M. de Montyon.-To the person who shall have shown the greatest merit in inventing or in improving this year: а instruments useful to the progress of agriculture, mechanical arts, and sciences, a gold medal of the value of 1500 francs. The prize will only be given to machines, the description and the plans or models of which, sufficiently detailed, shall have been submitted to the Academy, either 'separately, or in some printed work, transmitted to the Academy. Preservation from Lightning-Sir H. Davy, in his fourth lecture at the Royal Institution, recommends the following means of escaping the electric fluid during a thunder storm. He observed that in countries were thunder storms are frequent and violent, a walking cane might be fitted with a steel or iron rod to draw out at each end, one of which might be stuck into the ground, and the other end elevated eight or nine feet above the surface. The person who apprehends danger, should fix the cane and lie down a few yards from it. By this simple apparatus, the lightning descends down the wire into the earth, and secures him from injury. FROM THE EDINBURGÅ PAILOSOPHICAL JOURNAL. April 15.-A paper by Dr. Brewster was read at the Royal Society, 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 polarisation, 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 referrible 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. On Sounds excited in Hydrogen Gas. As the intensity of sound is diminished by the rarefication of the medium in which it is produced, it might have been expected that the sound in hydrogen gas would be feebler than when produced in atmospheric air in similar circumstances. Mr. Leslie, however, has found the difference to be actually much greater. Having placed within the receiver of an air-pump a small piece of clock-work by which a bell was struck every half minute the air was rarified, and after the reaction had been carried the length of 100 times, hydrogen gas was introduced. The sound, however, so far from being augmented, was at least as feeble as in atmospheric air of that extreme rarity, and decidedly much feebler than when formed in air of its own density, or rarified ten times. Mr. Leslie likewise observed the very curious fact that the mixture of hydrogen gas with atmospheric air, has a predominant influence in blunting or stifling sound. When one half of the volume of atmospheric air is extracted, and hydrogen gas admitted to fill up the vacant space, the sound will now become scarcely audible; an effect which he ascribes to a want of intimate combination between the two gases, which causes the pulsatory impressions to be dissipated before the sound is originally formed. [Mem. Cambridge Phil. Soc., vol. i. p. 267. Supposed Volcanoes in the Moon.-The luminous appearance in the moon, which Captain Kater and Mr. Dunlop observed on the 5th Feb. 1821, and which Captain Kater considered as a lunar volcano, was observed by Dr. Olbers, who thinks that there are no volcanoes in the moon, and that this phenomenon is capable of another explanation. It was situated, he observes, either in or near the spot marked Aristarchus, which is always enlightened by the earth, or the dark portion of the moon when three or four days old, and is distinguishable from all the other spots in the moon by its brightness. The luminous appearance, however, on the 5th of February was entirely different from the usual appearance of Aristarchus, and appeared with a five feet achromatic telescope like a star of the sixth magnitude. Canal Steam Navigation.-With a view to the introduction of steam vessels on canals, a very interesting experiment was made in the Union Canal at Edinburgh, on June 22, at two o'clock, with a large boat 28 feet long, constructed with an internal movement upon the principle of a model invented by Mr. Wright, and exhibited to a general meeting of the Highland Society of Scotland, in the month of January last. A committee appointed for the purpose by the directors of the Highland Society, attended to witness the experiment, and the chairman and most of the members of the Union Canal Company were also present. The boat had twenty-six persons on board; and although drawing fifteen inches of water, she was propelled by only four, men at the rate of between four and five miles an hour, while the agitation of the water, being confined entirely to the centre of the canal, was observed to subside long before it reached the banks, and consequently obviating its hitherto destructive tendency in washing them into the canal. [Star. On the Existence of Mercury in Sea-Water.-M. Proust has remarked, as M. Hilaire Rouelle did before him, that marine salt contains mercury. M. Proust has found mercury in every kind of muriatic acid that he has tried, and also in rock-salt. He suggests to navigators a method of ascertaining the existence of mercury in sea |
