were so bright as to allow the reading of the smallest print. At -the same time I observed a mass of clouds gathering in the northwest, the quarter to which the wind was blowing, and here the electrical appearances became peculiarly vivid, flashes of light

shifting rapidly among the broken intervals of the clouds, and near the horizon, assuming at times the appearance of a chain of light, which seemed to pass from a higher to a lower surface of cloud, and often continued to the eye for two or three seconds.

Sir Humphrey Davy's Discovery of a Method for preventing Explosions from the Fire Damp in Mines.

THE

HE numerous fatal effects of explosions in the collieries which have lately engaged the public attention, having induced the eminent chemical philosopher above-mentioned to turn his studies to the subject, the result has been a very curious and valuable paper communicated to the Royal Society, and printed in their Transactions for 1815, from which the following extract, chiefly referring to the practical part, has been made :

"After ascertaining, by a variety of experiments, the combustibility and explosive nature of the fire-damp in mines, and finding that a mixture of this gas with air would not explode in metallic canals or troughs when their diameter was less than one-seventh of an inch, and that explosions would not pass through such canals; also that explosions would not pass through very fine wire sieves or wire-gauze; Sir H. D. comes to the following inference.

"It is evident, then, that to prevent explosions in coal mines, it is only necessary to use air-tight lanterns, supplied with air from tubes or canals of small diameter, or from apertures covered with wire-gauze placed below the flame, through which explosions cannot be communicated, and having a chimney at the upper part, on a similar system, for carrying off the foul air; and common lanterns may be easily adapted to the purpose, by being made air-tight in the door and sides, by being furnished with the chimney, and the system of safety apertures below and above.

"The principle being known, it is easy to adopt and multiply practical applications of it.

"The first safe-lantern that I had constructed was made of tin-plate, and the light emitted through four glass plates in the sides. The air was admitted round the bottom of the flame from a number of metallic tubes of of an inch in diameter, and an inch and long.The chimney was composed of two open cones, having a common base perforated with many small apertures, and fastened to

the top of the lantern, which was made tight in a pneumatic rim containing a little oil; the upper and lower apertures in the chimney were about of an inch: the lamp, which was fed with oil, gave a steady flame of about an inch high, and half an inch in diameter. When the lantern was slowly moved, the lamp continued to burn, but more feebly; and when it was rapidly moved, it went out. To obviate this circumstance, I surrounded the bottom of the lantern with a perforated rim; and this arrangement perfectly answered the end proposed.

"I had another chimney fitted to this lantern, furnished with a number of safety tin-plate tubes of the sixth of an inch in diameter and two inches long; but they diminished considerably the size of the flame, and rendered it more liable to go out by motion; and the following experiments appear to show, that if the diameter of the upper orifice of the chimney be not very large, it is scarcely possible that any explosion produced by the flame can reach it.

"I threw into the safe-lantern with the common chimney, a mixture of 15 parts of air and one of fire-damp; the flame was immediately greatly enlarged, and the flame of the wick seemed to be lost in the larger flame of the fire. damp. I placed a lighted taper above the orifice of the chimney: it was immediately extinguished, but without the slightest previous increase of its flame, and even the wick instantly lost its fire by being plunged into the chimney.

"I introduced a lightedtaperinto a close vessel containing 15 parts

of air and one of gas_from_the distillation of coal, suffered it to burn out in the vessel, and then analysed the gas. After the carbonic acid was separated, it appeared by the test of nitrous gas to contain nearly of its original quantity of oxygen; but detonation with a mixture of equal parts of hydrogen and oxygen proved that it contained no sensible quantity of carburetted hydrogen gas.

"It is evident, then, that when, in the safe-lantern, the air gradually becomes contaminated with fire-damp, this fire-damp will be consumed in the body of the lantern; and that the air passing through the chimney cannot contain any inflammable mixture.

"I made a direct experiment on this point. I gradually threw an explosive mixture of fire-damp and air into the safe-lantern from a bladder furnished with a tube which opened by a large aperture above the flame; the flame became enlarged, and by a rapid jet of gas I produced an explosion in the body of the lantern; there was not even a current of air through the safety tubes at the moment, and the flame did not appear to reach above the lower aperture of the chimney; and the explosion merely threw out from it a gust of foul air.

I

"The second safety-lantern that have had made is upon the same principle as the first, except that instead of tubes, safety canals are used, which consist of close concentric hollow metallic cylinders of different diameters, and placed together so as to form circular canals of the diameter of from

to

of an inch, and an inch and long, by which air is admitted in

much larger quantities than by the small tubes. In this arrangement there is so free a circulation of air, that the chimney likewise may be furnished with safety canals.

"I have had lamps made for this kind of lantern which stand on the outside, and which may be supplied with oil and cotton with out any necessity of opening the lantern; and in this case the chimney is soldered to the top, and the lamp is screwed into the bottom, and the wick rises above the air canals.

"I have likewise had glass lamps with a single wick, and Argand lamps made on the same principle, the chimney being of glass cover ed with a metallic top containing the safety canals, and the air entering close to the flame through the circular canals.

"The third kind of safe lamp, or lantern, and which is by far the most simple, is a close lamp or lantern into which the air is admitted, and from which it passes, through apertures covered with brass wire gauze of of an inch in thickness, the apertures of which should not be more than

of an inch; this stops explosions as well as long tubes or canals, and yet admits of a free draught of air.

"Having succeeded in the construction, of safe-lanterns and lamps equally portable with common lanterns and lamps, which afforded sufficient light, and which bore motion perfectly well, I submitted them individually to prac tical tests, by throwing into them explosive atmospheres of fire dampand air. By the natural action of the flame drawing air through the air canals, from the explosive

atmosphere, the light was uni-. formly extinguished; and when an explosive mixture was forcibly pressed into the body of the lamp, the explosion was always stopped by the safety apertures, which may be said figuratively to act as a sort of chemical fire sieves in separating flame from air.

"When the fire-damp isso mixed with the external atmosphere as to render it explosive, the light in the safe-lantern or lamp will be extinguished, and warning will be given to the miners to withdraw from, and to ventilate that part of the mine.

"Ifit be necessary to be in a part of the mine where the fire-damp. is explosive, for the purpose of clearing the workings, taking away. pillars of coal, or other objects, the workmen may be lighted by a fire made of charcoal, which burns without flame, or by the steel-mill, though this does not afford such entire security from danger as the charcoal fire.

"It is probable, that when explosions occur from the sparks from the steel-mill, the mixture of the fire-damp is in the proportion required to consume all the oxygen of the air, for it is only in about this proportion that explosive mix tures can be fired by electrical sparks from a common machine.

"As the wick may be moved without communication between the air in the safe-lantern, or lamp, and the atmosphere, there is no danger in trimming or feeding them; but they should be lighted in a part of the mine where there is no fire-damp, and by a person charged with the care of the lights; and by these inventions, used with such simple precautions, there is

So early as the year 1801, a vessel propelled by steam was tried on the Forth and Clyde inland navigation, but was laid aside, among other reasons, on account of the injury it threatened the banks of the canal by the agitation of the water and as far as I can learn, the same objection still subsists to the use of steam-boats on artificial canals so narrow as those usual in Great Britain. That objection, however, I should think, does not apply to some of those of Holland and other countries on the continent.

The first attempt on any scale worthy of notice, to navigate by steam on the river Clyde, was in the

year 1812. A passage boat of about 40 feet keel and 10 feet beam, having a steam-engine of only three horses' power, began to ply on the river. Since that period the number of boats has gradually increased.

Besides three vessels which have left the Clyde, there are six at present plying on the river, two of which carry goods as well as passengers. They have on the whole

:

been gradually increased in tonnage as well as in the power of their engines; and still larger boats and more powerful engines are now constructing among others, one of about 100 feet keel and 17 feet beam with an engine of 24 horses' power; and one of equal burthen, having an engine of 30 horses' power. These boats are all neatly fitted up, and some of them even elegantly decorated.

On board all the passage steamboats are newspapers, pamphlets, books, &c. for the amusement of the passengers, and such refresh

ments as are desirable on so short a voyage, a distance of about 26 miles by water, and 24 by land.

The voyage betwixt Glasgow and Greenock, including stoppages at intermediate places, is commonly accomplished in from three to four hours, the vessels taking advantage of the tide as far as circumstances will permit : but as they start at different hours from the same place, they are sometimes obliged to go part or nearly the whole of their voyage. against the tide.

The voyage has been accomplished in 24 hours; the tide being favourable, but against a moderate breeze of contrary wind.

At first, owing to the novelty and apparent danger of the conveyance, the number of passengers was so very small that the only steam-boat then on the river could hardly clear her expenses: but the degree of success which attended that attempt soon commanded public confidence. The number of passengers which now go in those boats may seem incredible to those who have not witnessed it. Travelling by land has