said to be very moderate; and it is further stated to be the only process at present known, not even excepting sinking, which effec tually destroys the white ant.

13. Preservation of Butter.-M. Thenard recommends the method used by the Tartars, which consists in fuzing the butter in a waterbath at a temperature of 190° F., and retaining it quiescent in that state until the caseous matter has settled, and the butter become clear; it is then to be decanted, passed through a cloth, and cooled in a mixture of salt and ice, or, at least, in spring-water, without which it would crystallize, and not resist so well the action of air. Preserved in close vessels and cold places, it may be kept for six months as good as it was on the first day, especially if the upper part be excepted. If, when used, it be beaten up with one-sixth of cheese, it will have all the appearance of fresh butter. The flavour of rancid butter may, according to M. Thenard, be removed almost entirely by similar meltings and coolings.-Bull. Univ. D. xii. 155.

14. On the Dilatation of Stone, by M. Destigny (from the Mémoire de la Soc. libre d'Emul. de Rouen.)-The phenomena of dilatation by heat have been long known, and have been determined for a certain number of bodies. M. Destigny has extended this determination to the dilatation of stones observed by Bouguer in Peru, for bricks ; by George Juan, a Spaniard, quoted by M. Rondelet (Treatise on the Art of Building); and lastly, by M. Vicat, at the hewn stone bridge of Souillac. The precise extent of this dilatation was unknown. To obtain it, an instrument of extreme delicacy was required, and M. Destigny himself constructed one, founded upon the difference of dilatation of stone and iron, or copper. He selected for his experiments stones about 365 millimeters in length, 165 broad, and 50 thick, and fixed at one end a metallic rod, by means of a foot fixed in a copper plug let into the stone, while the other end of the rod rested against the small arm of a very sensible lever, which moved a needle iudicating the difference of dilatation. This small arm was 3 mm. long, the other 100 mm. This last moved. another lever, the length of the arms of which was 3 mm. for that against which it rested, and 100 mm. for the other, which was designed to point out on the arc of a circle, with a radius of 100 mm... the progress of the dilatation. The ratio of the space described between the small arm of the first lever, and the great arm of the second, was therefore as 1:1000. Transferring, then, the whole apparatus to a stove heated to 40, the dilatation must take place; and if it were the same for the stone and the metallic rod, the instrument would have indicated nothing; but the iron or the copper, having a much greater dilatation, put the small arm of the first lever in motion, and the amount of the difference of the dila tation might be read off on the arc of the circle. M. Destigny has thus found, for example, in one of his first experiments, the needle indicating 231.84 mm.

The copper rod, of which the dilatation is exactly known, would have made the index describe 301 mm. if it had been fixed to a body insensible to caloric. He deduces that the 69.16 mm. of difference is due to the stone. These experiments, repeated alternately on different stone bodies with a rod of copper, and with one of iron, have given the following results:

M. Destigny, wishing to know if the hygrometric state of the stone would produce any change in its dilatation, exposed to humidity a stone from St. Leu, and found that the dilatation was the same. One fact surprised him in this experiment,-it was the enormous quantity of water absorbed by the stone, almost amounting in volume to one-third of the stone itself.

The difference between the expansion of iron and stone accords with what was before known relative to the bad effects, and their causes, occasioned by introducing iron in certain situations into stone buildings. M. Destigny proposes to use compound and compensating bars of iron and copper for these purposes, but we doubt whether practice will sanction the suggestion.

15. New Artificial Horizon.-There are few more cumbersome instruments than the artificial horizon, in the manner in which it is usually constructed, so that an improved one, which we have seen with Mr. Newman, whose character for manufacturing the best philosophical apparatus is known to every friend of science in this country, promises to be of material advantage to the traveller. This instrument is comprised in a square box, the top of which is detached when the instrument is in use. The lower part contains the mercury, which is raised into the brass basin above by means of two screws, which previously kept together the parts of the box, acting upon a moveable bottom. The basin is rubbed over with nitrate of mercury, an invention of Professor Schumacher, of Altona, the effect of which is to make the quicksilver adhere to the sides of the basin, so that, with a little care, a perfectly level surface may be obtained, free from tremor, and well suited for the purpose for which it is required. By turning the screws, the quicksilver is then let down again into the reservoir; and the whole fulfils that indispensable condition in instruments designed for a traveller, that "the box shall not close unless all that it contains is locked, or the act of closing locks them,"

§ II. CHEMICAL SCIENCE.

!་ mba19709-it. 1. Application of a high Temperature to the Evaporation of Liquids. A maker of chloride of lime consulted M. Longchamp on the means of vaporizing a large quantity of muriatic acid, and the latter recommended a tube of platina. In a trial, one kilogramme (2.21 lbs.) of acid was vaporized in a tube 3 lines in diameter, and heated for 8 inches of its length. A larger apparatus was then made, consisting of a tube 2 inches in diameter, and 42 in length; but as 4 inches were external at one end, 2 at the other, and 4 were included in the sides of the furnace, only 32 inches in length were heated, equal to a capacity of 96 cubical inches. With this, 1 kilogramme of acid was evaporated in a minute, or 1500 kilogrammes in 24 hours. A trial was made to support the platina tube by one of cast iron, but the latter fused, and caused the former, which had become very brittle at the fusing part, to break; being, however, cut and repaired by soldering with gold, it was as good and effectual as at first.

From the effects produced, M. Longchamp concludes, that at high temperatures the evaporation is not in proportion to the heated surfaces, but in proportion to the capacity heated; that in a vessel heated to redness, it is 8 times greater than at the usual temperature employed, and that tubes of platina may be used to vaporize large quantities of muriatic acid.-Ann. des Sciences. Bull. Univ. A. xi. 353.

2. On the Specific Heat of Gases.—In a memoir on the specific heat of gases published some time since, MM. de la Rive and Marcet gave their results and conclusions, the latter being, that all gases had the same specific heat. The results have been a little objected to, as having been obtained upon quantities of gas too small, and the authors have therefore repeated their experiments on a larger scale, and given the full detail in a memoir published in the Bibliothèque Universelle, N.S. xli. p. 37. We shall probably return to this paper; in the mean time we give the conclusions, which are precisely the same as in the former case, namely

pro i. That at the same pressure, and in the same volume, all the gases have an equal specific heat.

ii. That in the same volume the same gas has a smaller specific heat, in proportion as it is subjected to a smaller pressure.

3. Artificial Preparation of Ice.-After numerous trials made by M. B. Meijlink with different salts, for the purpose of converting water contained in a tin vessel into ice, during their solution, he ultimately gave the preference to a mixture of 4 ounces nitrate of ammonia, 4 ounces sub-carbonate of soda, and 4 ounces of water. This mixture, in three hours, produced 10 ounces of ice; whilst with the mixture of sulphate of soda and muriate acid, he obtained ice only after 7 hours.

4. Odoriferous Lamp.-The peculiar property which Dobereiner discovered in spongy platina, of causing the union of hydrogen and oxygen with extreme facility, and at temperatures much below those ordinarily required for the purpose, led him to examine into the chemical changes analogous to combustion, which other bodies could undergo by the same or similar means, and he soon found that alcohol vapour in the open air, and under the influence of the prepared platina, became converted into acetic acid. The experiment then became nearly the same as that founded upon Sir H. Davy's discovery of the power of a heated platina wire, in continuing the combination of combustible bodies and supporters of combustion without flame; and it ultimately gave rise to the formation of a lamp, which, containing alcohol, and prepared at the place of the wick with a piece of spongy platina, or, as Dobereiner calls it, sub-oxide of platina, or some other form of that metal, gradually converted the whole of the alcohol into acetic acid.

The lamp in this form has been used for a night-lamp; it gives light enough to see the time by a watch held close to it, and if more light be required, a piece of amàdou may be carefully inflamed at it, and then a light procured in the usual way. M. Batka has proposed to use Eau de Cologne in place of common spirit of wine, and finds, that then the fragrance diffused is very grateful, being, in fact, occasioned by the actual formation of aromatic vinegar during the whole time the lamp burns. We doubt, however, whether a constant odour of this kind is desirable, unless indeed there be some bad smell to cover, and think that much more pleasure is derived from the inhalation of a perfectly pure and sweet atmosphere with the short occasional presence of fragrant odours, than from an atmosphere constantly, or for any long time aromatized.

5. Electricity of the Solar Rays.-(Letter from Sig. Carlo Mattrucci of Forli, to Professor Gazzeri.) "I hasten, Sir, to communicate to you some experiments which appear to me to deserve the attention of philosophers. Having been for a long time persuaded of the existence of electricity in the solar rays, I wished to ascertain the fact by experiment. Having for this purpose exposed to the sun a delicate condensing electrometer of gold leaf, I soon perceived the leaves diverge and open themselves also on that side of the glass case which was directly exposed to the solar action, as if they had been attracted by it. Being induced from this first fact to suspect glass in this situation electrified, I was anxious to know if this were the case: wherefore, having left some plates of it in the sun, in a few moments I touched them in different places with the ball of the electrometer, when a very perceptible divergence ensued, which, however, was much more apparent when I touched the plates, although lightly, with a flat surface, since the effects of the friction and the pressure did not afford a doubtful result. I con

cluded, then, that the solar rays had the power of electrifying glass, and it only remained for me to ascertain if this effect were owing to the real existence of electricity in these rays, or rather to the increased temperature of the glass, which I could easily determine by heating a plate of glass, and trying it with the electrometer. This I did several times, but never discovered any signs of electricity. I observed, also, that the glass plate exposed to the rays of the sun never became electric if placed beneath another glass plate, or if the face of the sun was obscured by the intervention of a cloud. These few experiments, which I have been induced to perform, seem to me sufficient to prove electricity in the solar rays. The influence of such a fact on the meteorological phenomena of terrestrial magnetism, and on so many other phenomena of nature, will, I hope, induce yourself and other philosophers to pursue the subject further."-Antologia, No. 100.

Forli, April 25, 1829.

Professor Saverio Barlocci of Rome, in a Memoir on the Influence of Solar Light, in the Production of Electric and Magnetic Phenomena, inserted in vol. xli. of the Giornale Arcadico, relates the following experiment he had performed, to ascertain the electric power of the solar light. Having decomposed it with a prism, he made the red ray and the violet ray fall upon two discs of blackened copper, each of which was attached to a copper wire. Two nuts of the same metal, sliding upon a vertical glass rod, and to which the two wires were attached, permitted their being brought near together, or removed at pleasure. Having suspended a prepared frog by the body to the upper wire, the legs were placed upon the lower one. The apparatus being thus arranged, whenever (the discs being respectively covered with the red and violet rays) a contact was formed between the extreme parts of the two wires, evident signs of contraction were observed in the frog.-Note by Prof. Gazzeri.

Having experimented two summers since, upon the solar spectrum, in exactly the same way, except that a very delicate galvanometer was used instead of a frog, no electricity could be obtained by means of an English sun.-M. F.

6. Atomic Weights of Iodine and Bromine.-The variation in the numbers given by different chemists for iodine induced M. Berzelius to experiment on the subject. Iodide of potassium was dissolved in very little boiling water, and a few drops of nitrate of silver added; the precipitate formed was redissolved by agitation, &c., and then the whole diluted with much cold water: an insoluble compound of silver fell down, which, if the iodide of potassium contained any chlorine, would evidently contain all that chlorine as chloride of silver. The purified and filtered solution was then precipitated by nitrate of silver, and the iodide of silver obtained, separated.