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USEFUL PROJECTS, &c.

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

THE 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 perfojated with many small apertures, and fastened to

the 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 -j- 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 scurcely possible that any explosion produced by the flame can reach it.

1 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 firedamp. 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.

1 introduced a lighted taper into a close vessel containing 15 parts

of air and one of gas fVmn 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 -J of its original quantity of oxygen; but detonation with a mixture of equal parti of hydrogen and oxygen proved that it contained no sensible quantity of carburetted hydrogen gas.

It is evident, then, that whea in the safe-lantern the air gradually becomes Contaminated with fire-damp, this fire-damp wul 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. 1 gradually threw an explosive mixture of fire-damp and air into the safe-lantern from a bladder furnished with a rube 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 flume 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.

The second safety-lantern that I 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 T'3 of on inch, and an inch and T's

long,

long, by which air is admitted in much larger quantities than by the email 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 without any necessity of opening the lantern ; and in this case the chimney is soldered to the top, and the lump is screwed into the bottom, and the wick rises above the air canals.

1 have likewise had glass lamps ■with a single wick, and Argand lamps made on the same principle, the chimney being of glass covered 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 Tie of an inch in thickness, the apertures of which should not be more than i47 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 practical tests, by throwing into them explosive atmospheres of firedamp and air. By the natural action of the flame drawing air through

the air canals, from the explosive atmosphere, the light Was' uniformly extinguished; and when an explosive mixture was forcibly pressed into the body of the lamp, the explosion wa* 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 is so 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.

If it 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 mixtures 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

euch such simple precautions, there is every reason to believe a number of lives will be saved, and much misery prevented. Where candles are employed in the open air in the mines, life is extinguished by the explosion; with the safe-lantern or safe-lamp, the light is only put out, and Ho other inconvenience will occur.

ON STEAM-BOATS UPON THE CLYDE.

By Robertson Buchanan, Esq. of

GUtsgaw. (From Mr.TUloch'sPhilosophical Magazine.)

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 fur as 1 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 IS 12. A passage boat of about.40 feet keel and 10i feet beam, liaving 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 engine are now constructing: among others, one of about lOOfeetked 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 refreshments as are desirable on so short a voyage, a distance of about % miles by water, and 24 by land

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

The voyage has been acro»plishedin 2* hours; the tide bong favourable, but against a moderate bre?ze of contrary wind.

At first, owing to the novelty and apparent danger of the conveyance, the number of passengers was so very small that tw only steam-boat then on the m« could hardly clear her expense: but the degree of success Woks attended that attempt soon commanded public confidence. I* number of passengers which now go in those boats may seem incre" dible to those who have not witnessed it. Travelling by land bn

not

not only been nearly superseded, but the communication very greatly increased, owing to the cheapness and facility of the conveyance. Many days, in fine weather, from 500 to 600 have gone from Glasgow to Port-Glasgow and Greenock, and returned in the same day. One of the boats alone has been known to carry 247 at one time. The increase of travelling in consequence of navigation by steam, may be estimated by the number that went in the common passage-boats before the introduction of this agent: at that time, the highest estimate even for summer did not much exceed 50 up and 50 down, and those generally of the lower class of the people. The number that then went by coaches may be thus estimated: four coaches up and four down, which might average sue passengers each.

In the summer, the pleasure of the voyage and the beauty of the scenery attract multitudes; and the bathing-places below Greenock have, in consequence of the easy passage, been crowded beyond former example.

The scenery near Glasgow is sylvan and beautiful, but becomes bolder and more picturesque as the river descends, until it terminates in the rugged mountains of the west Highlands.

CHINESE PASTE.

(From Dr. Thomson's AnnnU of)
Philosophy.

The method of making paste in China is much more economical than the mode followed in this country. Were it universally

adopted by trunk-makers, bookbinders, and others, who use great quantities of paste, it would produce a very material saving of flour, which in years of scarcity might be of the greatest consequence. The following formula used in China was lately communicated to the Right Hon. Sir Joseph Banks, Bart, by a gentleman at present in Canton.—Mix together bullock's blood and quick lime, in the proportion of one pound of the latter to lOlbs. of the former. It becomes a stiff jelly, in which state it is sold to the consumers, who beat it down with an addition of water into a state sufficiently fluid for use. At Canton it will keep live or six days in the hot weather and ten or twenty days in the cold. In Britain it would probably keep longer.

NEW MODE OF MANUFACTURING HEMP AND FLAX.

(From the Same.)

About two years ago Mr. Lee took out a patent for obtaining hemp and flax directly from the plants by a new method. He has established a manufactory for the purpose at Old Bow, on the river Lea, near London, where his method, and the result of it may be seen. I consider Mr. Lee's invention as the greatest improvement ever introduced into the linen business, and as likely to occasion a total change in the wholeofourbleaeh-fields. Hitherto the only way of obtaining hemp and flax has been to steep the plants in water till they •begin to rot. They arc then exposed for

some

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