the jar. Atmospheric air being again admitted into the receiver, the mercury entered into the jar, and the elastic fluid condensed into a liquid on its surface. This liquid was chloro-cyanic acid. It possessed the following properties.

It is colourless. Its smell is very strong, exciting tears. It reddens litmus, is not inflammable, and does not detonate when mixed with twice its bulk of oxygen or hydrogen gas. The specific gravity of its vapour is 2.111. Its solution in water does not precipitate nitrate of silver nor barytes water. The alkalies absorb it completely. When an acid is poured into this solution the chlorocyanic acid is decomposed, and converted into muriatic acid, carbonic acid, and ammonia. This acid being composed of a volume of chlorine united to a volume of cyanogen, without any diminution of bulk, is analogous to muriatic acid, hydriodic acid, and dydrocyanic acid, only the chlorine performs the part of the hydrogen which constitutes the acidifying principle in these last acids.

IX. Dr. Murray, of Edinburgh's, Method of preventing Explosions in Coal-Mines from Fire-Dump.

At the second meeting of the Royal Society of Edinburgh for the winter session, a paper was read, by Dr. Murray, on a plan for lighting mines so as to guard against explosions from the kindling of fire-damp. It had been before explained to several scientific Gentlemen, and announced in the public papers; and an outline of it had been transmitted to Newcastle, where a very favourable opinion had been expressed with regard to it. The leading idea on which it is founded is, that the inflammable gas constituting fire-damp accumulates in the roof of the passages and workings of the mine, mingling with the atmospheric air, and at length forming a mixture, which is exploded by coming in contact with the candles or lamps of the miners; and that this mixture can never accumulate so as to fill the whole space, at least while the mine is worked, for the miner would become affected by breathing the carbureted hydrogen gas, independent of other appearances which would indicate its presence. The simple means of security, therefore, against its explosion, is to bring the air to sustain the flame of the lamp or candle from the floor of the mine; and this is easily done, by burning the lamp within a glass case, having a small aperture at the top to admit of the escape of the heated air and smoke, of such a size that the current shall always pass outwards, and thus prevent any of the external air from entering by it, and having attached to the under part of it a tube reaching to the floor of the mine to convey the air to the flame. In the fixed lamps this tube may be of iron or copper; and moveable lamps, which the miner can carry in the hand, may be constructed with a flexible tube of prepared leather, varnished, of such a length as to reach to the floor.

Besides the security given by this apparatus by bringing the air to support the flame from the floor of the mine, it has other means of security one in particular, Dr. M. remarked, is the rarefaction of the air within the case; whence, if even any mixture of inflam

mable air were to enter, there is little or no probability that it would be inflamed. He referred to the experiments of Grotthus, as proving that mixtures of inflammable gases with atmospheric air, or even with oxygen gas, cannot be inflamed if they are in a certain degree of rarefaction: and he quoted the observations of Dr. Thomson, that the exploding power of carbureted hydrogen is not considerable, that a certain proportion of it with atmospheric air is necessary to enable it to inflame, and that no mixture of fire-damp with atmospheric air can be made to explode out of the mine. In the small quantity, therefore, in which it must be within the lamp, in its rarefied state from the heat, and with a diluted atmosphere, there is no probability whatever that it would be inflamed: and by properly adjusting the size of the aperture, this might even be carried so far that, instead of inflaming, it would weaken or extinguish, the flame; and still more, if ever inflammation or detonation should take place within the lamp, there would be no chance of this being communicated to the air of the mine. If, notwithstanding all these means of security, danger should be dreaded in any particular situation, it might be effectually guarded against by conveying pure air from the bottom of the shaft through an iron tube, which by upright tubes might communicate both with the fixed and moveable lamps. This, however, would probably be seldom neces

sary.

The accumulation of the fire-damp, when it occurred, would be indicated by its smell, or by its effect on respiration; and if it ever proceeded to that extent, by its effect in weakening the flame of the lamp; and when suspected, could be easily ascertained by more accurate trials. Its discharge can be effected by opening a more perfect ventilation, or by the application of a steam-engine, or an exhausting machine.

This method Dr. M. suggested might even be applied with safety so as to light the mines with great economy and advantage by coal gas. The same method admits also of being used with equal effect to guard against choak-damp, the other deleterious gas which occurs in mines and other situations. His paper will be speedily published.

*The author of the paper on the " Relation between the Specific Gravity of Gaseous Bodies and the Weight of their Atoms" thinks it proper to state, that many of the numbers in the fourth table in that paper, which are stated to be given on the authority of Berzelius, will be found to differ from those given by that chemist in the Annals, v. iii. p. 362, on account of their having been founded on the deductions of others, (principally of Dr. Thomson) from the experiments of Berzelius, and not upon that chemist's own deductions.

The following note by Dr. Henry arrived too late to be inserted in that part of his paper where he speaks of Mr. Parkes :

"It is but justice to Mr. Parkes to state, that I am far from suspecting him of the intentional suppression of any fact respecting the history of the new method of bleaching; and that I believe his account to be a faithful one, so far as his means of information extended."

Hygr. at

1815. Wind. Max. Min. Med. Max. Min. | Med.

9 a. m. Rain,

The observations in each line of the table apply to a period of twenty-four hours, beginning at 9 A. M. on the day indicated in the first column. A dash denotes, that the result is included in the next following observation.

REMARKS.

Tenth Month.-25. Lightning to the N. and W. last evening. 27. The wind changed to N. E. this morning: Cumulastratus, with inosculation, a. m.: west, p. m. 28. wet, a. m.: fair, p. m.; rain again at night: windy. 29. A brisk gale at N. E. continued through the day and night: a bank of Cumulastratus was visible in the morning in the S., from which quarter Cumuli were propagated northwards, changing the state of the superior clouds as they advanced: some Cirri in long lines above the whole were not affected: a solar halo appeared from one to two, p. m., and the sky was turbid beneath the sun. 30. a. m. completely overcast : windy, drizzling at intervals. 31. a. m. Cirrostratus tending to Cirrocumulus, beneath large Cirri pointing N. E. and S. W.: fair.

Eleventh Month.-1. Low Cumulastratus beneath Cirrostratus: a breeze at N. E., changing at night to N. W., without affecting the state of the clouds, which were dense, p. m. 2. Breeze at N. W.: a. m. Barometer very steady: Cumulastratus : much redness in the twilight. 3. a. m. clear, with Cirrostratus: slight hoar frost: coloured sun-set. 4. a. m, clear, with a little Cirrostratus: very white hoar frost, with ice: a fine day: after sun-set, a dull purple in the E,, with a little orange in the W.: the moon conspicuous, the crescent indifferently defined, and pale. 5. Rain by seven, a. m.: after which low Cumulastratus. 6. a. m. A few drops, with the wind S.: then fine. 7. Cloudy: rain: lunar corona. 8. Some drops, a. m.: then much Cirrostratus: sun-set, with streaks of brown and purple on a yellow ground: moon visible, but its light peculiarly dim: wind and rain in the night. 9. Wet morning: dripping day lunar corona: wind. 10. Fair, with Cirrostratus. 11. A little rain at night : Cirrostratus. 12. A fair warm day: various clouds passed over with a moderate wind: at evening the moon showed a Jucid corona: to which succeeded, (the wind having risen and veered to S.) a continued exhibition of coloured halos varying in diameter, formed on low, rapidly passing, curling clouds, with an occasional corona, of pale green or yellow, between: a most tempestuous night followed, with rain. 13. Windy: a shower, p.m.: the moon gold-coloured. 14, Clear: wind moderate. 15. Cloudy, a. m.: windy a sensible odour of electricity in the air, at one, p. m. morning: fair, p.m. 17. a. m. White frost: little of yesterday's snow remaining: the wind S. W.; a breeze; a little rain: p. m. a waggon from the north came thickly covered with snow: wind brisk at N. at night. 18. Hoar frost: the moon looks like a map, so great is the transparency of the higher atmosphere. 19. Hoar frost and rime on the trees, bodies of thin mist, probably Cirrostratus, moved quickly over us this morning from the S. W. rendering the tree tops invisible: a fine day: Cirrus and Cirrostratus at night. 20. a. m. Cumulastratus: max. temp. at nine. 21. a. m. Cirrus: Cirrostratus: min. temp. at nine, 22. Fair, with boar frost.

RESULTS.

16. A snowy

Prevailing Winds Northerly, interrupted by a Southerly current, which greatly depressed the barometer, soon after the middle of the period, and was followed by a sharp frost,

INDEX.