Chapter 7

Fig. 111.Fig. 111.

a.Flask containing water, and producing steam, which passes to the iron tube,b b, containing the iron borings heated red hot in the charcoal stovec. The hydrogen passes to the jard, standing on the shelf of the pneumatic trough.

If bottles of hydrogen gas are prepared by all the processes described, they will present the same properties when tested under similar circumstances. A lighted taper applied to the mouths of the bottles of hydrogen, which should be inverted, causes the gas to take fire with a slight noise, in consequence of the mixture of air and hydrogen that invariably takes place when the stopper is removed; on thrusting the lighted taper into the bulk of the gas it is extinguished, showing that hydrogen possesses the opposite quality to oxygen—viz., that it takes fire, but does not support combustion. By keeping the bottles containing the hydrogen upright, when the stopper is removed the gas escapes with great rapidity, and atmospheric air takes its place, so much so that by the time a lighted taper is applied, instead of the gas burning quietly, it frequently astonishes the operator with a loud pop. This sudden attack on the nerves may be prevented by always experimenting with inverted bottles. (Fig. 112.)

Fig. 112.Fig. 112.

a.Bottle opened upright, and hydrogen exploding.b.Bottle opened inverted, and hydrogen burning quietly at the mouth.

Hydrogen is 14.4 lighter than air, and for that reason may be passed into bottles and jars without the assistance of the pneumatic trough. One of the most amusing proofs of its levity is that of filling paper bags or balloons with this gas; and we read, in the accounts of the fêtes atParis, of the use of balloons ingeniously constructed to represent animals, so that a regular aerial hunt was exhibited, with this drawback only, that nearly all the animals preferred ascending with their legs upwards, a circumstance which provoked intense mirth amongst the volatile Frenchmen. The lightness of hydrogen may be shown in two ways—first, by filling a little gold-beater's skin balloon withpurehydrogen (prepared by passing the gas made from zinc and dilute pure sulphuric acid through a strong solution of potash, and afterwards through one of nitrate of silver), and allowing the balloon to ascend; and then afterwards, having of course secured the balloon by a thin twine or strong thread, it may be pulled down and the gas inhaled, when a most curious effect is produced on the voice, which is suddenly changed from a manly bass to a ludicrous nasal squeaking sound. The only precautions necessary are to make the gas quite pure, and to avoid flame whilst inhaling the gas. It is related by Chaptal that the intrepid (quære, foolish) but unfortunate aeronaut, Mons. Pilate de Rosio, having on one occasion inhaled hydrogen gas, was rash enough to approach a lighted candle, when an explosion took place in his mouth, which he says "was so violent that he fancied all his teeth were driven out." Of course, if it were possible to change by some extraordinary power the condition of the atmosphere in a concert-room or theatre, all the bass voices would become extremely nasal and highly comic, whilst the sopranos would emulate railway whistles and screech fearfully; and supposing the specific gravity of the air was continually and materially changing, our voices would never be the same, but alter day by day, according to the state of the air, so that the "familiar voice" would be an impossibility.

A bell rung in a gas jar containing air emits a very different sound from that which is produced in one full of hydrogen—a simple experiment is easily performed by passing a jar containing hydrogen over a self-acting bell, such as is used for telegraphic purposes. (Fig. 113.)

Fig. 113.Fig. 113.

a.Stand and bell.b b.Tin cylinder full of hydrogen, which may be raised or depressed at pleasure, by lifting it with the knob at the top, when the curious changes in the sound of the bell are audible.

Some of the small pipes from an organ may be made to emit the most curious sounds by passing heavy and light gases through them; in these experiments bags containing the gases should be employed, which may drive air, oxygen, carbonic acid, or hydrogen, through the organ pipes at precisely the same pressure.

One of those toys called "The Squeaking Toy" affords another and ridiculous example of the effect of hydrogen on sound, when it is used in a jar containing this gas. (Fig. 114.)

Fig. 114.Fig. 114.

The squeaking toy, used in a jar of hydrogen.

An accordion played in a large receptacle containing hydrogen gas demonstrates still more clearly what would be the effect of an orchestra shut up in a room containing a mixture of a considerable portion of hydrogen with air, as the former, like nitrogen, is not a poison, and only kills in the absence of oxygen gas.

Some very amusing experiments with balloons have been devised by Mr. Darby, the eminent firework manufacturer, by which they are made to carry signals of three kinds, and thus the motive or ascending power may be utilized to a certain extent.

Mr. Darby's attention was first directed to the manufacture of a good, serviceable, and cheap balloon, which he made of paper, cut with mathematical precision; the gores or divisions being made equal, and when pasted together, strengthened by the insertion of a string at the juncture; so that the skeleton of the balloon was made of string, the whole terminating in the neck, which was further stiffened with calico, and completed when required by a good coating of boiled oil. These balloons are about nine feet high and five feet in diameter in the widest part, exactly like a pear, and tapering to the neck in the most graceful and elegant manner. They retain the hydrogen gas remarkably well for many hours, and do not leak, in consequence of the paper of which they are made being well selected and all holes stopped, and also from the circumstance of the pressure being so well distributed over the interior by the almost mathematical precision with which they are cut, and the careful preparation of the paper with proper varnish. One of their greatest recommendations is cheapness; for whilst a gold-beater's skin balloon of the same size would cost about 5l., these can be furnished at 5s.each in large quantities.

A balloon required to carry one or more persons must be constructed of the best materials, and cannot be too carefully made; it is therefore a somewhat costly affair, and as much as 200l., 500l., and even 1000l.have been expended in the construction of these aerial chariots.

The chief points requiring attention are:—first, the quality of the silk; secondly, the precision and scrupulous nicety required in cuttingout and joining the gores; thirdly, the application of a good varnish to fill up the pores of the silk, which must be insoluble in water, and sufficiently elastic not to crack.

The usual material is Indian silk (termed Corah silk), at from 2s.to 2s.6d.per yard.

Thegoresor parts with which the balloon is constructed require, as before stated, great attention; it being a common saying amongst aeronauts, "that a cobweb will hold the gas if properly shaped" the object being to diffuse the pressure equally over the whole bag or balloon.

The varnish with which the silk is rendered air-tight can be made according to the private recipe of Mr. Graham, an aeronaut, who states that he uses for this purpose two gallons of linseed oil (boiled), two ditto (raw), and four ounces of beeswax; the whole being simmered together for one hour, answers remarkably well, and the varnish is tough and not liable to crack.

For repairing holes in a balloon, Mr. Graham recommends a cement composed of two pounds of black resin and one pound of tallow, melted together, and applied on pieces of varnished silk to the apertures.

The actual cost of a balloon will be understood from information also derived from Mr. Graham. His celebrated "Victoria Balloon," which has passed through so many hairbreadth escapes, was sixty-five feet high, and thirty-eight feet in diameter in the broadest part; and the following articles were used in its construction:—

£s.d.1400 yards of Corah silk, at 2s.6d.per yard17500The netting weighed 70 lbs.2000Extra ropes weighed 20 lbs. at 2s.per lb.200The car weighed 25 lbs.700Varnish, wages, &c.1600————————————£22000

Thirty-eight thousand cubic feet of coal gas were required to fill this balloon, charged by one company 20l., by others from 9l.to 10l.; and eight men were required to hold the inflated baggy monster.

Such a balloon as described above is a mere soap bubble when compared with the "New Aerial Ship" now building in the vicinity of New York; the details are so practical and interesting, that we quote nearly the whole account of this mammoth or Great Eastern amongst balloons, as given in theNew York Times.

"An experiment in scientific ballooning, greater than has yet been undertaken, is about to be tried in this city. The project of crossing the Atlantic Ocean with an air-ship, long talked of, but never accomplished, has taken a shape so definite that the apparatus is already prepared and the aeronaut ready to undertake his task.

"The work has been conducted quietly, in the immediate vicinity of New York, since the opening of spring. The new air-ship, which hasbeen christened the City of New York, is so nearly completed, that but few essentials of detail are wanting to enable the projectors to bring it visibly before the public.

"The aeronaut in charge is Mr. T. S. C. Lowe, a New Hampshire man, who has made thirty-six balloon ascensions.

"The dimensions of the City of New York so far exceed those of any balloon previously constructed, that the bare fact of its existence is notable. Briefly, for so large a subject, the following are the dimensions:—Greatest diameter, 130 feet; transverse diameter, 104 feet; height, from valve to boat, 350 feet; weight, with outfit, 3½ tons; lifting power (aggregate), 22½ tons; capacity of gas envelope, 725,000 cubic feet.

"The City of New York, therefore, is nearly five times larger than the largest balloon ever before built. Its form is that of the usual perpendicular gas-receiver, with basket and lifeboat attached.

"Six thousand yards of twilled cloth have been used in the construction of the envelope. Reduced to feet, the actual measurement of this material is 54,000 feet—or nearly 11 miles. Seventeen of Wheeler and Wilson's sewing machines have been employed to connect the pieces, and the upper extremity of the envelope, intended to receive the gas-valve, is of triple thickness, strengthened with heavy brown linen, and sewed in triple seams. The pressure being greatest at this point, extraordinary power of resistance is requisite. It is asserted that 100 women, sewing constantly for two years, could not have accomplished this work, which measures by miles. The material is stout and the stitching stouter.

"The varnish applied to this envelope is a composition the secret of which rests with Mr. Lowe. Three or four coatings are applied, in order to prevent leakage of the gas.

"The netting which surrounds the envelope is a stout cord, manufactured from flax expressly for the purpose. Its aggregate strength is equal to a resistance of 160 tons, each cord being capable of sustaining a weight of 400 lbs. or 500 lbs.

"The basket which is to be suspended immediately below the balloon is made of rattan, is 20 feet in circumference and 4 feet deep. Its form is circular, and it is surrounded by canvas. This car will carry the aeronauts. It is warmed by a lime-stove, an invention of Mr. O. A. Gager, by whom it was presented to Mr. Lowe. A lime-stove is a new feature in air voyages. It is claimed that it will furnish heat without fire, and is intended for a warming apparatus only. The stove is 1½ feet high, and 2 feet square. Mr. Lowe states that he is so well convinced of the utility of this contrivance, that he conceives it to be possible to ascend to a region where water will freeze, and yet keep himself from freezing. This is to be tested.

"Dropping below the basket is a metallic lifeboat, in which is placed an Ericsson engine. Captain Ericsson's invention is therefore to be tried in mid-air. Its particular purpose is the control of a propeller, rigged upon the principle of the screw, by which it is proposed to obtaina regulating power. The application of the mechanical power is ingeniously devised. The propeller is fixed in the bow of the lifeboat, projecting at an angle of about forty-five degrees. From a wheel at the extremity twenty fans radiate. Each of these fans is 5 feet in length, widening gradually from the point of contact with the screw to the extremity, where the width of each is 1½ feet. Mr. Lowe claims that by the application of these mechanical contrivances his air-ship can be readily raised or lowered, to seek different currents of air; that they will give him ample steerage way, and that they will prevent the rotatory motion of the machine. In applying the principle of the fan, he does not claim any new discovery, but simply a practical development of the theory advanced by other aeronauts, and partially reduced to practice by Charles Green, the celebrated English aeronaut.

"Mr. Lowe contends that the application of machinery to aerial navigation has been long enough a mere theory. He proposes to reduce the theory to practice, and see what will come of it. It is estimated that the raising and lowering power of the machinery will be equal to a weight of 300 lbs., the fans being so adjusted as to admit of very rapid motion upward or downward. As the loss of three or four pounds only is sufficient to enable a balloon to rise rapidly, and as the escape of a very small portion of the gas suffices to reduce its altitude, Mr. Lowe regards this systematic regulator as quite sufficient to enable him to control his movements and to keep at any altitude he desires. It is his intention to ascend to a height of three or four miles at the start, but this altitude will not be permanently sustained. He prefers, he says, to keep within a respectable distance of mundane things, where 'he can see folks.' It is to be hoped his machinery will perform all that he anticipates from it. It is a novel affair throughout, and a variety of new applications remain to be tested. Mr. Lowe, expressing the utmost confidence in all the appointments of his apparatus, assured us that he would certainly go, and, as certainly, would go into the ocean, or deliver a copy of Monday'sTimesin London on the following Wednesday. He proposes to effect a landing in England or France, and will take a course north of east. A due easterly course would land him in Spain, but to that course he objects. He hopes to make the trip from this city to London in forty-eight hours, certainly in sixty-four hours. He scouts the idea of danger, goes about his preparations deliberately, and promises himself a good time. As the upper currents, setting due east, will not permit his return by the same route, he proposes to pack up the City of New York, and take the first steamer for home.

"The air-ship will carry weight. Its cubical contents of 725,000 feet of gas suffice to lift a weight of 22½ tons. With outfit complete its own weight will be 3½ tons. With this weight 19 tons of lifting power remain, and there is accordingly room for as many passengers as will care to take the venture. We understand, however, that the company is limited to eight or ten. Mr. Lowe provides sand for ballast, regards his chances of salvation as exceedingly favourable,places implicit faith in the strength of his netting, the power of his machinery, and the buoyancy of his lifeboat, and altogether considers himself secure from the hazard of disaster. If he accomplish his voyage in safety, he will have done more than any air navigator has yet ventured to undertake. If he fail, the enterprise sinks the snug sum of 20,000 dollars. Wealthy men who are his backers, sharing his own enthusiasm, declare failure impossible, and invite a patient public to wait and see."

A night ascent witnessed at any of the public gardens is certainly a stirring scene, particularly if the wind is rather high. On approaching the balloon, swayed to and fro by the breeze, it seems almost capable of crushing the bold individual who would venture beneath it; seen as a large dark mass in the yet dimly-lighted square, it appears to be incapable of control; when the inflation is completed, the aeronaut, all importance, seats himself in the car, and blue lights, with other fireworks, display the victim who is to make a "last ascent," or perhapsdescent. Finally the word is given, the ropes are cast off, and the bulky chariot rises majestically to the sound of the National Anthem. The crowd see no more, but the next day'sTimesreports the end of the aerial journey.

Balloons can never be of any permanent value as means of locomotion until they can be steered; and this is a problem, the solution of which is something likeperpetual motion. In the first place, a balloon of any size exposes an enormous surface to the pressure and force of the winds; and when we consider that they move at the rate of from three to eighty miles per hour, it will be understood that the fabric of the balloon itself must give way in any attempt to tear, work, or pull it against such a force. Secondly and lastly, the power has not yet been created which will do all this without the inconvenience of being soheavythat the steering engine fixes the balloon steadily to the earth by its obstinate gravity. When engines of power are constructed without the aeronaut's obstacle of weight—when balloons are made of thin copper or sheet-iron, then we may possibly hear of the voyage of the good shipAerial, bound for any place, and quite independent of dock, port, and the host of dues (quere), which the sea-going ships have to disburse. It is, however, gratifying to the zeal and perseverance of those who dream of aerial navigation, to know that a balloon is not quite useless; and here we may return to the consideration of Mr. Darby's signals, which are of various kinds, and intended to appeal to the senses by night as well as by day; and first, byaudible sounds. Such means have long been recognised, from the ancient float and bell of the "Inchcape Rock," to the painful minute-gun at sea, or the shrill railway whistle and detonating signals employed to prevent the horrors of a collision between two trains. The signal sounds are produced by the explosion of shells capable of yielding a report equal to that of a six-pounder cannon, and they are constructed in a very simple manner. A ball, composed of wood or copper, and made up by screwing together the two hemispheres, is attached to a shaft or tail of cane or lance-wood, properly feathered like an arrow; at the side opposite to that of the arrow—viz., at its antipodes, is placed a slight protuberancecontaining a minute bulb of glass filled with oil of vitriol, and surrounded with a mixture of chlorate of potash and sugar, the whole being protected with gutta-percha, and communicating by a touch-hole with the interior, which is of course filled with gunpowder. These shells are attached to a circular framework by a strong whipcord, which passes to a central fuse, and are detached one after the other as the slow fuse (made hollow on the principle of the argand lamp) burns steadily away. Directly a shell falls to the ground, the little bulb containing the oil of vitriol breaks, and the acid coming in contact with the chlorate of potash and sugar, causes the mixture to take fire, when the gunpowder explodes. During the siege of Sebastopol many similar mines were prepared by the Russians in the earth, so that when an unfortunate soldier trod upon the spot, the concealed mine blew up and seriously injured him; such petty warfare is as bad as shooting sentries, and a cruel application of science, that unnecessarily increases the miseries of war without producing those grand results for which the truly great captains, Wellington and Napoleon, only warred. (Fig. 115.)

Fig. 115.Fig. 115.

a.Ring attached to balloon, carrying an hexagonal framework with six shells.b.Hollow fuse, which burns slowly up to the strings, and detaches each shell in succession.c.Section of shell. The shaded portion represents the gunpowder.

The bill distributor consists of a long piece of wood, to which areattached a number of hollow fuses, with packets of bills, protected from being burned or singed by a thin tin plate; 10,000 or 20,000 bills can thus be delivered, and the wind assists in scattering them, whilst the balloon travels over a distance of many miles. It must be recollected that in each case the shells and the bills are detached by the string burning away as the fire creeps up from the fuse. (Fig. 116.)

Fig. 116.Fig. 116.

The bill distributor, consisting of three hollow fuses, with bills attached in packets.

Another most ingenious arrangement, also prepared by Mr. Darby, is termed by the inventor, the "Land and Water Signal," and may be thus described:—A short hollow ball of gutta-percha, or other convenient material, five or six inches in diameter, and filled with printed bills, or the information, whatever it may be, that is required to be sent, is attached to a cap to which a red flag, having the words "Open the shell" and four cross sticks, canes, or whalebones with bits of cork at equal distances, are fitted. The whole is connected by a string to the fuse as before described. These signals are adapted for land and water: in either case they fall upright, and in consequence of the sticks projecting out they float well in the water, and can be seen by a telescope at a distance of three miles. (Fig. 117.) Many of these signals were sent away by Mr. Darby from Vauxhall; one was picked up at Harwich, another at Brighton, a third at Croydon; in the latter case it was found by a cottager, who, fearing gunpowder and combustibles, did not examine the shell, but having mentioned the circumstance to a gentleman living near him, they agreed to cut it open; and intelligence of their arrival, in this and the other cases, was politely forwarded to Mr. Darby at Vauxhall Gardens.

Fig. 117.Fig. 117.

The land and water signal, which remains upright on land, or floats on the surface of water.a.The water-tight gutta-percha shell, containing the message or information.b b b.Sticks of cane to keep the flag in an upright position; at the ends are attached cork bungs.

Balloons, like a great many other clever inventions, have been despised by military men as new-fangled expedients, toys, which may do very well to please the gaping public, but are and must be useless in the field. Over and over again it has been suggested that a balloon corps for observation should be attached to the British army, but the scheme hasbeen rejected, although the expense of a few yards of silk and the generation of hydrogen gas would be a mere bagatelle as compared with the transport and use of a single 32-pounder cannon. The antiquated notions of octogenarian generals have, however, received a great shock in the fact that the Emperor Napoleon III. was enabled, by the assistance of a captive balloon, to watch the movements and dispositions of the Austrian troops; and with the aid of the information so obtained, he made his preparations, and was rewarded by the victory of Solferino; and as soon as the battle was over Napoleon III. occupied at Cavriana the very room and ate the dinner prepared for his adversary, the Emperor Francis Joseph.

Over and over again the most excellent histories have been written of aerostation, but they all tend to one truth, and that is, the great danger and risk of such excursions; and to enable our readers to form their own judgment, a chronological list of some of the most celebrated aeronauts, &c., is appended.

1675. Bernair attempted to fly—killed.1678. Besnier attempted to fly.1772. L'Abbé Desforges announced an aerial chariot.1783. Montgolfier constructed the first air balloon." Robertsfrères, first gas balloon, destroyed by the peasantry ofGeneva, who imagined it to be an evil spirit or the moon.1784. Madame Thiblé, the first lady who was ever up in the clouds;she ascended 13,500 feet." Duke de Chartres, afterwardsEgalitéOrleans, travelled 135miles in five hours in a balloon." Testu de Brissy, equestrian ascent." D'Achille, Desgranges, and Chalfour—Montgolfier balloon." Bacqueville attempted a flight with wings." Lunardi—gas balloon." Rambaud—Montgolfier balloon, which was burnt." Andreani—Montgolfier balloon.1785. General Money—gas balloon, fell into the water, and not rescuedfor six hours." Thompson, in crossing the Irish Channel, was run into with thebowsprit of a ship whilst going at the rate of twenty milesper hour." Brioschi—gas balloon ascended too high and burst the balloon;the hurt he received ultimately caused hisdeath." A Venetian nobleman and his wife—gas balloon—killed." Pilatre de Rozier and M. Romain—gas balloon took fire—bothkilled.1806. Mosment—gas balloon—killed." Olivari—Montgolfier balloon—killed.1808. Degher attempted a flight with wings.1812. Bittorf—Montgolfier balloon—killed.1819. Blanchard, Madame—gas balloon—killed.1819. Gay Lussac—gas balloon, ascended 23,040 feet above the level ofthe sea. Barometer 12.95 inches; thermometer 14.9 Fah." Gay Lussac and Biot—gas balloon for the benefit of science.Both philosophers returned safely to the earth.1824. Sadler—gas balloon—killed." Sheldon—gas balloon." Harris—gas balloon—killed.1836. Cocking—parachute from gas balloon—killed.1847. Godard—Montgolfier balloon fell into and extricated from theSeine.1850. Poitevin, a successful French aeronaut." Gale, Lieut.—gas balloon—killed." Bixio and Barral—gas balloon." Graham, Mr. and Mrs.—gas balloon.—Serious accident ascendingnear the Great Exhibition in Hyde Park." Green, the most successful living aeronaut of the present time.

Of the 41 persons enumerated, 14 were killed, and nearly all the aeronauts met with accidents which might have proved fatal.

Fig. 118.Fig. 118.Flying machine (theoretical).

Flying machine (theoretical).

Soap bubbles blown with hydrogen gas ascend with great rapidity, and break against the ceiling; if interrupted in their course with a lighted taper they burn with a slight yellow colour and dull report.

By constructing a pewter mould in two halves, of the shape of a tolerably large flask, a balloon of collodion may be made by pouring the collodioninsidethe pewter vessel, and taking care that every part is properly covered; the pewter mould may be warmed by the external application of hot water, so as to drive off the ether of the collodion, and when quite dry the mould is opened and the balloon taken out. Such balloons may be made and inflated with hydrogen by attaching to them a strip of paper, dipped in a solution of wax and phosphorus, and sulphuret of carbon; as the latter evaporates, the phosphorus takes fire and spreads to the balloon; which burns with a slight report. The pewter mould must be very perfectly made, and should be bright inside; and if the balloons are filled with oxygen and hydrogen, allowing a sufficient excess of the latter to give an ascending power, they explode with a loud noise directly the fire reaches the mixed gases.

In a soup-plate place some strong soap and water; then blow out a number of bubbles with a mixture of oxygen and hydrogen; a loud report occurs on the application of flame, and if the room is small the window should be placed open, as the concussion of the air is likely to break the glass.

Any noise repeated at least thirty-two times in a second produces a musical sound, and by producing a number of small explosions of hydrogen gas inside glass tubes of various sizes, the most peculiar sounds are obtained. The hydrogen flame should be extremely small, and the glass tubes held over it may be of all lengths and diameters; a trial only will determine whether they are fit for the purpose or not.

Flowers, figures, or other designs, may be drawn upon silk with a solution of nitrate of silver, and the whole being moistened with water, is exposed to the action of hydrogen gas, which removes the oxygen from the silver, and reduces it to the metallic state.

In like manner designs drawn with a solution of chloride of gold are produced in the metallic state by exposure to the action of hydrogen gas. Chloride of tin, usually termed muriate of tin, may also be reduced in a similar manner, care being taken in these experiments thatthe fabric upon which the letters, figures, or designs are painted with the metallic solution be kept quite damp whilst exposed to the hydrogen gas.

A mixture of two volumes of hydrogen with one volume of oxygen explodes with great violence, and produces two volumes of steam, which condense against the sides of the strong glass vessel, in which the experiment may be made, in the form of water. As the apparatus called the Cavendish bottle, by which this experiment only may be safely performed, is somewhat expensive, and requires the use of an air-pump, gas jars with stop-cocks, and an electrical machine and Leyden jar, other and more simple means may be adopted to show the combination of oxygen and hydrogen, and formation of water.

If a little alcohol is placed in a cup and set on fire, whilst an empty cold gas jar is held over the flame, an abundant deposition of moisture takes place from the combustion of the hydrogen of the spirits of wine. Alcohol contains six combining properties of hydrogen, with four of charcoal and two of oxygen. If a lighted candle, or an oil, camphine, Belmontine, or gas flame, is placed under a proper condenser, large quantities of water are obtained by the combustion of these substances (Fig. 119).

Fig. 119.Fig. 119.

a.A burning candle, or oil or gas lamp. Copper head and long pipe fitting intob c, the receiver from which the condensed water drops intod.e e.Two corks fitted, between which is folded some wet rag.

During the combustion of a mixture of two volumes of hydrogen with one of oxygen, an enormous amount of heat is produced, which is usefully applied in the arrangement of the oxy-hydrogen blowpipe. The flame of the mixed gases produces little or no light, but when directed on various metals contained in a small hole made in a fire brick, a most intense light is obtained from the combustion of the metals, which is variously coloured, according to the nature of the substances employed. With cast-iron the most vivid scintillations are obtained, particularly if after having fused and boiled the cast-iron with the jet of the two gases, one of them, viz., the hydrogen, is turned off, and the oxygen only directed upon the fused ball of iron, then the carbon of the iron burns with great rapidity, the little globule is enveloped in a shower of sparks, and the whole affords an excellent notion of the principle of Bessemer's patent method of converting cast-iron at once into pure malleable iron, or by stopping short of the full combustion of carbon, into cast-steel.

The apparatus for conducting these experiments is of various kinds, and different jets have been from time to time recommended on account of their alleged safety. It may be asserted that all arrangements proposed for burning any quantity of themixedgases are extremely dangerous: if an explosion takes place it is almost as destructive as gunpowder, and should no particular damage be done to the room, there is still the risk of the sudden vibration of the air producing permanent deafness. If it is desired to burn themixedgases, perhaps the safest apparatus is that of Gurney; in this arrangement the mixed gases bubble up through a little reservoir of water, and thus the gas-holder—viz., a bladder, is cut off from the jet when the combustion takes place. (Fig. 120.) This jet is much recommended by Mr. Woodward, the highly respected President of the Islington Literary and Scientific Institution, and may be fitted up to show the phenomena of polarized light, the microscope, and other interesting optical phenomena.

Fig. 120.Fig. 120.

Gurney's jet.a. Pipe with stop-cock leading from the gas-holder.b. The little reservoir of water through which the mixed gases bubble.c.The jet where the gases burn.d.Cork, which is blown out if the flame recedes in the pipe,c.

Mr. Woodward states, that a series of experiments, continued during many years, has proved, that while the bladder containing the mixed gases is under pressure, the flame cannotbe madeto pass the safety chambers, and consequently an explosion is impossible; and even if through extreme carelessness or design, as by the removal of pressure or the contact of a spark with the bladder, an explosion occurs, it can produce no other than the momentary effect of the alarm occasioned bythe report; whereas, when the gases are used in separate bags under a pressure of two or three half hundredweights, if the pressure on one of the bags be accidentally removed or suspended, the gas from the other will be forced into it, and if not discovered in time, will occasion an explosion of a very dangerous character; or if through carelessness one of the partially emptied bags should be filled up with the wrong gas, effects of an equally perilous nature would ensue.

Fig. 121.Fig. 121.

a.The bladder of mixed gases, pressed by the board,b b, attached by wire supports to another board,c c, which carries the weights,d d.e e.Pipe to which the bladder,a, is screwed, and whenais emptied, it is re-filled from the other bladder,r.f f f.Pipe conveying mixed gases to the lantern,g g, where they are burnt from a Gurney's jet,h.

In the oxy-hydrogen blowpipe usually employed, the gases are kept quite separate, either in gasometers or gas bags, and are conveyed by distinct pipes to a jet of very simple construction, devised by the late Professor Daniell, where they mix in very small volumes, and are burnt at once at the mouth of the jet. (Fig. 122.)

Fig. 122.Fig. 122.

Daniell's jet.o o.The stop-cock and pipe conveying oxygen, and fitting inside the larger tubeh h, to which is attached a stop-cock,h, connected with the hydrogen receiver.a.The orifice near which the gases mix, and where they are burnt.

The gases are stored either in copper gasometers or in air-tight bags of Macintosh cloth, capable of containing from four to six cubic feet of gas, and provided with pressure boards. The boards are loaded with two or three fifty-six pound weights to force out the gas with sufficientpressure, and of course must be equally weighted; if any change of weight is made, the stop-cocks should be turned off and the light put out, as the most disastrous results have occurred from carelessness in this respect. (Fig. 123.)

Fig. 123.Fig. 123.Fig. 123. Gas bag and pressure boards.

Fig. 123. Gas bag and pressure boards.

The oxy-hydrogen jet is further varied in construction by receiving the gases from separate reservoirs, and allowing them to mix in the upper part of the jet, which is provided with a safety tube filled with circular pieces of wire gauze. (Fig. 124.) With this arrangement a most intense light is produced, called the Drummond or lime light, and coal gas is now usually substituted for hydrogen.

Fig. 124.Fig. 124.

a a.Board to whichb bis fixed.o.Oxygen pipe.h.Hydrogen pipe.c c.Space filled with wire gauze.d.Lime cylinder.

There are many circumstances that will cause the union of oxygen and hydrogen, which, if confined by themselves in a glass vessel, may be preserved for any length of time without change; but if some powdered glass, or any other finely-divided substance with sharp points, is introduced into the mixed gases at a temperature not exceeding 660° Fahrenheit, then the gases silently unite and form water.

This curious mode of effecting their combination is shown in a still more interesting manner by perfectly clear platinum foil, which if introduced into the mixed gases gradually begins to glow, and becoming red-hot causes the gases to explode. Or still better, by the method first devised by Dobereiner, in 1824, by which finely prepared spongy platinum—i.e., platinum in a porous state, and exposing a large metallic surface—is almost instantaneously heated red-hot by contact with the mixed gases. When this fact became known, it was further applied to the construction of an instantaneous light, in which hydrogen was made to play upon a little ball of spongy platinum, and immediately kindled. These Dobereiner lamps were possessed by a few of the curious, and would no doubt be extensively used if the discovery of phosphorus had not supplied a cheaper and more convenient fire-giving agent. When the spongy platinum is mixed with some fine pipeclay, and made into little pills, they may (after being slightly warmed) be introduced into a mixture of the two gases, and will silently effect their union. The theory of the combination is somewhat obscure, and perhaps the simplest one is that which supposes the platinum sponge to act as a conductor of electric influences between the two sets of gaseous particles; although, again, it is difficult to reconcile this theory with the fact that powdered glass at 660°, a bad conductor of electricity, should effect the same object. The result appears to be due to some effects of surface by which the gases seem to be condensed and brought into a condition that enables them to abandon their gaseous state and assume that of water.

When Sir H. Davy invented the safety-lamp, he was aware that, in certain explosive conditions of the air in coal mines, the flame of the lamp was extinguished, and in order that the miner should not be left in the dreary darkness and intricacies of the galleries without some means of seeing the way out, he devised an ingenious arrangement with thin platinum wire, which was coiled round the flame of the lamp, and fixed properly, so that it could not be moved from its proper place by any accidental shaking. When the flame of the safety-lamp, having the platinum wire attached, was accidentally extinguished by the explosive atmosphere in which it was burning, the platinum commenced glowing with an intense heat, and continued to emit light as long as it remained in the dangerous part of the mine. Sir H. Davy warned those who might use the platinum to take care that no portion of the thin wire passedoutsidethe wire gauze, for the obvious reason that, if ignited outside the wire gauze protector, it would inflame the fire-damp.

Water is decomposed by passing a current of voltaic electricity through it by means of two platinum plates, which may be connected with a ten-cell Grove's battery. The gases are collected in separate tubes, and the experiment offers one of the most instructive illustrations of the composition of water. (Fig. 125.)

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