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1817.] M. Regnault has found that the mud of the river Nile, dried in the sun, consists of the following ingredients:

Water, 11

Carbon, 9

Oxyde of Iron, 6

Silex, 4.

Carbonate of Magnesia, 4

Carbonate of Lime, 18

Alumine, 48

100

Dr Edwards has lately made some curious though cruel experiments upon the submersion, suffocation, and strangulation of frogs, toads, and salamanders. Some of these animals, when kept in very dry air, died immediately; others of them lived many days, though immersed in thick coatings of plaster of Paris; while others gave signs of life even 15 days after they were strangled and decapitated, a complete cicatrization of the wound occasioned by decapitation having taken place. Dr Edward's memoir on this subject was highly approved by a commission of the Institute, who engaged him to continue his inquiries.

Optical Structure of Ice.—We understand that Dr Brewster, when examining the optical properties of ice, has found, that even large masses, two or three inches thick, formed upon the surface of standing Water, are as perfectly crystallized as rock crystal, or calcareous spar, all the axes of the elementary crystals corresponding with the axes of the hexaedral prisms being exactly parallel to cash other, and perpendicular to the horizontal surface. This unexpected result was obtained by transmitting polarized light through a plate of ice, in a direction perpendicular to its surface. A series of beautiful concentric coloured rings, with a dark rectangular cross passing through their centre, were thus exhibited, and were of the opposite nature to those which Dr B. had some years ago discovered in beryl, the ruby, and other minerals.—Brande's Journal of Science, vol. iv. p. 155.

A Lactometer, for ascertaining the comparative value of each cow's milk in a dairy, has lately been laid before the Oxfordshire Agricultural Society, by Mr Fane. The apparatus consists of tubes of glass about half an inch in diameter, and eleven inches long, fixed upright in a wooden frame, each tube having a line round it exactly ten inches from the bottom. Each tube is filled up to this line at milking time, with the milk of a cow; after standing twelve hours, the cream is measured by a scale of ten parts to an inch, and as the whole depth of the milk and cream is ten inches, each division will represent one per cent, of the whole.

Curious compound of Platinum—Mr Davy, professor of chemistry in the Cork Institution, while pursuing some investigations on platinum, formed a peculiar compound of this metal, which has some remarkable properties. When it comes in contact with the vapour of alcohol at the common temperature of the air, there is an immediate chemical action, the platinum is reduced to the metallic state, and the heat produced is sufficient to ignite the metal, and to continue it in a state of ignition. It would at present be premature to offer any conjectures on the uses to which this new compound may be applied; but from the peculiar properties, both of the metal and the compound, there is reason to believe it will admit of some important applications. Mr Davy has already employed it as a simple and easy means of affording heat and light. To produce heat, nothing more is necessary than to moisten any porous animal, vegetable, or mineral substance, as sponge, cotton, asbestos, iron filings, sand, &c. with alcohol or whisky, and let a bit of the compound fall on the substance so moistened; it instantly becomes red hot, and continues to remain so whilst any spirit remains; nor is it extinguished by exposure to the atmosphere, or by blowing the breath on it; on the contrary, partial currents of air only make the ignited metal glow brighter. The heat produced in this way may be accumulated to a considerable extent, by increasing the quantity of the materials employed. On these facts, Mr Davy has constructed a sort of tinder-box that answers very well to procure immediate light. The box contains two small phials, and some sulphur matches tipped at the points with a very minute bit of phosphorus; one of the phials contains the compound, the other a little alcohol The phials may either have glass stopples or corks. The stopper of the phial containing the alcohol has a small aperture at the bottom, in which there is inserted a bit of sponge; this is kept moistened but not quite wet with alcohol. When a light is wanted, it is only necessary to take out the stopper, and put a bit of the compound no bigger than the head of a pin on the moistened sponge; it instantly becomes red hot, and will immediately light one of the matches.

This mode of igniting a metal, and keeping it in a constant state of ignition, is quite a novel fact in the history of chemistry, and affords a happy illustration of the facts pointed out by Sir Humphry Davy, in his late able and scientific researches, which have thrown so much light on the philosophy of flame, led to such brilliant and highly important results, and will probably admit us to a more intimate acquaintance with nature in her refined and elaborate operations.

The attention of scientific men at Liverpool has recently been much engaged by a young woman, named Margaret M'Avoy, who became blind in June 1816, in consequence of a disorder in the head, supposed to be water in the brain; and who, if we may believe the reports of credible witnesses,