the metallic appearance, invariably produced by the fusion of a mixture of silica with animal oil, was wanting; silica mixed with alcohol, spirits of turpentine, naphtha, &c. was readily fused into a transparent glass, analogous to that obtained in the last experiment. Although the preceding experiments were instituted for the purpose of ascertaining the nature of the metallic substance produced by the fusion of silica combined with oil, we are obliged to confess that they appear to throw but little light on the subject; for if, as Dr. Thomson suggests, the metallic appearance is occasioned by the charcoal contained in the animal oil, why should it not also be obtained by the fusion of other substances when mixed with oil? on the other hand, from the impossibility of producing a metallic appearance from the silica when moistened with other fluids, the origin of this metallic substance is still involved in obscurity. We should, therefore, esteem it a particular favour if Dr. Clarke (through the medium of your work) would favour us with his ideas on the subject; and we beg permission to ask that gentleman, whether the metallic substance he denominates silicium was decomposed when submitted to the action of water, the nitric, muriatic, or nitromuriatic acids. I have the honour to remain, Gentlemen,

XI. Employment of Sir H. Davy's Safety-Lamps in Flanders. An interesting pamphlet has lately appeared at Mons, on the explosions that take place in coal-mines, and on the means of preventing them, by the use of Sir H. Davy's safety-lamps; it is published under the direction of the chamber of commerce and manufactures of Mons, accompanied by notes, and by the results of a series of experiments, that were conducted by M. Gossart, President of the Chamber.

The province of Hainault is said to be more rich in coal-mines than any other part of the continent of Europe, and to have no less than 100,000 persons employed in the working them. The same kind of dangerous accidents occurred in them as in the north of England, and various expedients had been employed for their prevention, which were, however, but little effectual in obviating the evil.

"All the precautions," the reporter observes, "which were hitherto known or had been practised, had not been able to preserve, in all cases, the unfortunate workmen from the terrible effects of the explosion of the gas which is extricated in the mines. It is then an inappreciable benefit which we confer, by making known the method of preventing these accidents, equally simple and infallible, which has been discovered by the celebrated Humphry Davy."

M. Gossart gives an ample and accurate detail of the nature and properties of the carburetted hydrogen gas which is extri

cated in the coal mines, and correctly describes the experiments of Sir H. Davy, by which he ascertained the high temperature necessary for the inflammation of this gas, and the consequent means of preventing the inflammation, when the gas has its temperature lowered by passing through any cooling medium, a circumstance which eventually led to the construction of the safety-lamp in its present form. It appears to have been as useful in the mines of Flanders as in those of England, since no accident of any kind has occurred there since it has been adopted, nor has any inconvenience or difficulty been experienced with respect to it. The pamphlet can scarcely be said to contain any information that is new to us in this country; but it must be regarded a valuable document, in as much as it affords an independent evidence in favour of the value of the instrument, and displays the high sense of obligation to Sir H. Davy which is acknowledged in other countries.

XII. Infirmary for Diseases of the Eye.

Sir William Adams having been nominated by his Majesty's government to superintend that part of York Hospital, Chelsea, which has been appropriated to the reception of the blind pensioners belonging to the army, navy, and artillery, feels it a duty to lay open to the profession at large his new modes of treating them. This duty is suggested as well by the pecular confidence which has been reposed in him, as by the high sanction thus conferred upon his improvements in ophthalmic surgery. He, therefore, freely invites all medical practitioners, and students, who are interested in the advancement of this branch of surgery, to attend his operations at York Hospital; which, for their convenience, will be performed in future on Tuesdays and Fridays, between the hours of seven and nine in the morning.

To remove all doubt, or misconception, with regard to Sir William Adams's practice, he proposes, on each of these days, to give a description of the nature of one of the diseases to be operated upon the general modes of performing the operation his peculiar mode-and his reasons for deviating from the usual practice, where such deviation has been found necessary.

The records kept of each case, from the patient's admission into the Hospital to his final discharge, will be open at the periods already mentioned, for the inspection of such gentlemen as attend; so that the profession will be enabled fairly to appreciate the character of the new as compared with the old modes of practice.

Erratum.

In the letter of Philo-chemicus Cantabrigiensis, in our last number, the word sphericle is erroneously printed for spherule.

ARTICLE XIX.

Magnetical and Meteorological Observations.
By Col. Beaufoy, F.R.S.

Bushey Heath, near Stanmore.

Latitude 51° 37′ 42′′ North. Longitude west in time 1′ 20.7".

This month was remarkable for the violence of the wind and the unsettled state of the magnetic needle, which most days vibrated some minutes; on the 17th the oscillation amounted to 22′ 50′′. Rain, by the pluviameter, between noon on March 1, and on April 1, 2-330 inches. Evaporation, during the same period, 2.57 inches.

Table containing the Mean Monthly Variation of the Magnetic Needle, from the Beginning of April, 1817, to the End of March, 1818.

By inspecting the table, it appears that the noon variation (with the exception of the month of August) decreased from April to November, and afterwards increased; which circumstance renders it doubtful if the variation be yet arrived at its maximum.