We copy the above notice from a long letter on the subject given by Baron Zach (X. p. 104.) without expressing any opinion on so extraordinary a circumstance. It is strange that the three observations should have been made at the same hour and minute, and at exact intervals of ten days.

9. Astronomical and Trigonometrical Surveys in Russia.-The liberal and enlightened patronage which the Emperor Alexander has extended to science in general, and to useful knowledge of every kind, is nowhere more conspicuous than in the numerous astronomical and trigonometrical surveys which he has ordered throughout his extensive dominions.

Prince Wolkonsky, since he received the direction of the Etat Major of Russia, has placed all the surveys upon a fixed and excellent system. The survey of the government of Wilna, under the direction of MajorGeneral de Tenner, has been carried on by the methods used in France for the measurement of an arc of the meridian, and the trigonometrical part has been for some time completed. General Tenner measured with Delambre's apparatus two bases, one near Driswiat, on the ice, and the other near Ponedeli, each of which was nearly 30,000 English feet long. Nearly the third part of the government of Wilna is surveyed topographically, on a scale of 1; and in five years the whole will be completed. The astronomical observations were made by M. Wisnieffsky, who has been employed for several years in determining the positions of many points in Russia. Major-General de Schubert has been carrying on, since 1820, the survey of the government of Petersburg. He has finished the triangles from Narva to the Ladoga, and has continued them as far north as the frontiers of Finland. He has measured a base of 33888,86 English feet at Slavancka, near Zarskoe-Selo. The scale of this survey is to be 1 The English foot is adopted in these surveys,

the English inch being equal to 200 sagenes, or saschenes.

M. Struve proposes to connect his triangulations for an arc of the me◄ ridian with those of General Tenner at Dunabourg; and General Schubert expects to connect his with them at Hochland.-See Zach's Corr. Astron. ix. p. 171.

10. Dr. Tiark's Astronomical Expedition.-This expedition is, we understand, employed by the Board of Longitude to sail to Heligoland, Edinburgh, and the Nase of Norway, to settle the longitude of these points, and connect our reckonings with those of the Continent.

OPTICS.

11. On a singular Scintillation of the Stars.-On Sunday the 12th Oct. 1823, at 4h. A. M. Baron Zach (Corr. Astron. vol. ix. p. 301.) observed at Genoa a very remarkable scintillation of the stars, which astonished all who saw it. The stars seemed to throw out sparks and jets of flame with surprising rapidity and vivacity. The same effects were seen by every person, and also through an achromatic opera glass, so that the phenomenon must have had its origin in the atmosphere, and was, we

think, owing to a want of homogeneity in the aerial medium, similar to what takes place in mixing alcohol and water.

Baron Zach observed another very curious fact, which surprised him more than the preceding phenomenon. When the observer fixed his eye steadily upon any star, its scintillations became more settled and tranquil; but the stars seen at the corner of the eye, or by indirect vision, became more disorderly and rapid in their scintillations. Baron Zach states, that he has sought in vain all our works on optics for an explanation of this effect.

The laws of indirect vision upon which this curious fact depends, have been investigated and explained by Dr. Brewster in a paper on the Eye, read before the Royal Society of Edinburgh on the 3d Dec. 1822. In that paper he has shown, that bodies seen by indirect vision alternately vanish and reappear even when seen with both eyes, and that they assume colours different from their natural ones, certain colours vanishing in preference to others.

12. Direction of the Axes of Double Refraction.-M. Fresnel informs us, in the Bull. Philom. 1824, p. 40, that M. Mitscherlich has found that in some salts, such as Sulphate of Magnesia, the one resultant axis is more inclined than the other to the faces of cleavage, or crystallized without any appearance of a defect of symmetry in the crystalline forms.

The same fact has been observed in the Brazil Topaz, and described by Dr. Brewster in the Cambridge Transactions, vol. ii. p.,5; but he attributes it to peculiarities of crystallization.

13. On the Phosphorescence of several Sub-resins.-M. Bonastre, who has made some interesting experiments on this subject, has given the name of sub-resins to those which are entirely deprived of essential oil; which are deprived of acid; and which are soluble only in boiling alcohol, ether, or the volatile oils. The property of phosphorescence, when they were pounded in a porcelain mortar with a glass pestle, he found in gum Elemi, gum Alouchi and the gum Arbol-a-brea from Manilla. In gum Elemi the light was pale and feeble, and less than is shown in pounding sugar. In gum Alouchi, well dried and heated, the light was much more vivid, and the colour a little reddish. It gave out slight scintillations. The gum Arbol-a-brea was more luminous than sugar, and even emitted light by friction in water. When these three gums were treated with Dilute Sulphuric Acid, they were phosphorescent in the same degree. See the Journal de Pharmacie, Avril 1824, p. 193.

MAGNETISM.

14. Gay Lussac on the mutual action of two magnetic Particles in different Bodies.-This very interesting experiment was undertaken by M. Gay Lussac at the request of M. Poisson, (see p. 356.) for the purpose of ascertaining whether or not the mutual action of two magnetic particles depended on the matter of each of the bodies; which was found to be the case.

A magnetical needle, eight inches long, was found to make ten horizontal vibrations near the direction of the magnetic meridian in 131 seconds. A prismatic bar of soft iron, about eight inches long, ths of an inch wide, and th thick, in a vertical direction, was now fixed at the distance of two inches below the needle, and in the plane of the magnetic meridian. The oscillations of the needle became more frequent, being about 10 in 65 seconds, and soon after 10 in 60 seconds.

A similar and equal bar of pure nickel was now substituted in place of the iron bar, and the needle made at first 10 oscillations in 78 seconds, and soon after 10 in 77 seconds. When the bar of nickel was removed, the needle made 10 oscillations in 130 seconds by the action of the earth alone.-M. Poisson's Memoir on Magnetism.

ELECTRICITY.

15. Berzelius's Method of distinguishing Positive and Negative Electricity. When the electric current passes by means of a point to the tongue, the positive electricity is acid, and the negative electricity a more caustic acid, or as it were alkaline.

16. Production of electricity in freezing water.-M. Grotthus has found, that when water is frozen rapidly in a Leyden jar, the outside coating not being insulated, receives a weak electrical charge, the inside being positive, and the outside negative. When the ice is rapidly thawed, the inside is negative, and the outside positive.

METEOROLOGY.

17. Simonoff on the diurnal variation of the Barometer.-From 4316 observations on the barometer, made in the Great Pacific Ocean, and at Taiti, M. Simonoff concluded that the lowest height of the mercury took place at 3h. 24′ P. M. and 3h. 18′ A. M. and the greatest height at 9h. 24' A. M. and 9h. 30' P. M. M. Simonoff accompanied Admiral Bellinghausen in the Russian expedition to the South Polar Regions.

18. Comparison of Spirit of Wine and Mercurial Thermometers.-A set of very important observations on this subject have been recently made by M. Flauguergues of Viviers, with peculiar care and attention. The spirit of wine thermometer was one made under the eye of Reaumur himself, by his pupil the Abbé Nollet, and the mercurial ones were octogesimal, and made by the best modern artists. The experiments were often repeated.

Temperatures.

Mixture of two parts of pounded ice, and one part by

weight of muriate of soda,

Mixture of two parts of pounded ice, and one part of muriate of ammonia,

Mixture of two parts of pounded ice, and one part of
crystallized sugar,

Two parts pounded ice, and one nitre,
Melting ice,

Temperatures.

Well, 34 feet deep. Mean of six years' observation,

Cellar,

Human heat,

Fusion and coagulation of yellow wax,

Boiling alcohol, of the density 0.851; the barometer

Boiling mixture of three parts of the above alcohol,
and one part of rain water, for the liquor used for
Reaumur's thermometer; the barometer at 28 inches,
See Zach's Corresp. Astron. Vol. ix. No. 5. p. 435.

II. CHEMISTRY.

19. Minerals produced by Heat.-It has been very often observed, that the analyses of minerals are of comparatively little value, as long as we are not capable of reproducing by composition what had been dissolved. Professor Mitscherlich has accomplished this important object. We have been gratified by the sight of beautiful and welldefined crystals of grayish-white pyroxène, which had been obtained by mixing the constituent parts indicated by analysis in the necessary proportion, and exposing this mixture to the high degree of heat of the porcelain furnaces of Sèvres. By this means, Professor Mitscherlich has succeeded in obtaining several species that occur in nature. He has likewise observed among the different kinds of slags more than forty species in a crystallized state, particularly of such minerals as are found in primitive rocks, but likewise a good many others which have not hitherto been observed. We propose giving in our next number a full statement of the farther details of these most important experiments.

20. Analysis of Copper green from Somerville, New-Jersey, by Mr. Bowen.

21. Berzelius's Analysis of the Sulphato-tri-carbonate of Lead.-This eminent chemist, in analysing some specimens of this interesting mineral, sent to him for this purpose by Dr. Brewster, obtained the following results:

In the letter with which M. Berzelius has favoured us on this subject, he remarks, that his result accords with that of Mr. Irving of Edinburgh, who found the carbonate of lead to be 73, and the sulphate 29, giving an excess of 2.0. (Edin. Phil. Journal, vol. vi. p. 388.) He likewise re

marks, that as he had an excess of 1.1 of weight of the stone, it is probable that a part of the oxide of lead in it is in the form of a subsalt. "The result," he adds, "as it is, does not agree with the definite proportions; and the small quantity of the mineral did not permit me to make ulterior experiments."

Mr. Brooke, in his analysis, makes the results agree perfectly with the definite proportions, (Edin. Journ. iii. 118.) viz. about 72.5 of carbonate, and 27.5 of sulphate of lead. He had no excess of weight, and

did not observe either the trace of muriatic acid or of lime.

22. Ammonia disengaged from Plants during Vegetation.-M. Chevallier has determined the very curious fact, that the Chenopodium vulvaria spontaneously disengages ammonia in a very free state during the act of vegetation; and he has also found, in conjunction with M. Boullay, that a great number of flowers, even among those which have a very agreeable odour, spontaneously disengage ammonia during vegetation. M. Chevallier likewise obtained ammonia from the Chenopodium vulvaria by distillation. (See the Journal de Pharmacie, Feb. 1824, p. 100.)

23. Influence of Prussic Acid upon Vegetation.-M. C. J. Th. Becker, in his Dissertatio de Acidi Hydrocyanici vi perniciosa in Plantas, which ap peared at Jena in 1823, in 4to. has performed a number of experiments, from which it follows that the Prussic acid, prepared according to Vauquelin's method, destroys vegetable life in nearly the same manner as it acts upon animals. Grains immersed in this acid die, or lose their germinating faculty. The more delicate vegetables yield to it more readily than the robust ones.

24. Benzoic Acid in the Oil of Dahlia.-M. Payen having obtained an essential oil from the Dahlia, has determined, by numerous experiments, that it contains two substances, and that the crystallizable matter presents several of the characters of Benzoic acid.

25. Cyanuret of Iodine.-M. Serullas has discovered this new compound, which consists of azote, carbon and iodine. It is obtained by heating an intimate mixture of two parts of cyanuret of mercury, and one part of iodine, when both are quite dry. It has a strong and penetrating odour. Its taste is caustic. It neither alters paper of tournesol nor that of curcuma. When thrown upon a burning coal, it exhales abundantly violet vapours. M. Serullas considers it as composed of iodine 82.8, and cyanogen 17.2.-Journ. de Pharm. Mai, 1824, p. 257.

26. Composition of Fulminic Acid.-M. Liebig has found that the fulminating silver of Howard owes its detonating property to an acid capable of combining in different proportions with different bases, and of thus forming as many detonating salts. MM. Gay Lussac and Liebig having examined this fulminic acid, have found that this substance which cannot be obtained in an insulated state, is composed of one atom of cyanogen, and one atom of oxygen, forming probably together the