an instrument for directing the flame of a lamp or candle horizontally, so as to communicate an intense heat to small bodies placed in the flame. This is effected by impelling with velocity through a small aperture, against the flame, a stream of air, by means of the muscles of respiration and the mouth, or by a bellows. The blow-pipe is used in soldering, by the jeweller and goldsmith, and other artists, who fabricate small objects of metal; by the glass-blower, in making thermometers and barometers, and other instruments formed from the tubes which are obtained from the glass-house; by the enameller; and also in glass-pincheng, which is the art of forming glass in a mould fixed on a pair of pincers, into the ornamental pendants for glass lustres. This is one of the many ingenious processes carried on at Birmingham. The glass-blower, the enameller, and the glass-pincher, work their blow-pipe with the blast of a pair of bellows. As the process of soldering requires a shorter continuance of the blast, the blow-pipe for this purpose is blown by the mouth. By the mineralogist and chemist, the blow-pipe is used as an instrument for extemporaneous analysis in the dry way.

Fig. 1, Plate CIX., is the common blow-pipe used in different soldering; it is of brass. Fig. 2 is Dr Wollaston's blow-pipe, which is composed of three tubes of brass, of an elongated conical form, which are made to fit stiff and air-tight into each other when in use, and the two smaller pack into the largest; so that the instrument, when not in use, occupies a very small space, and may be carried in the pencil-case of a common pocket-book. This, with a piece of platina-foil, two or three inches long, to hold the object of experiment to the flame, constitutes a commodious dokimastic apparatus for the travelling mineralogist. The three parts of the tube are represented, packed the one within the other, at A, separate at B, and put together ready for use at C, fig. 2.

A second division of blow-pipes consists of those which have a cavity for the purpose of retaining the humidity of the breath, which, without this precaution, collects into drops when the blowing is continued long, and is at last driven upon the matter under operation so as to cool it. They are of various forms; see figures 3, 4, 5, 6, 7; and have been contrived for the purposes of the chemist and mineralogist. Fig. 3 is of glass or of metal. Fig. 4 is of brass or of silver, containing no alloy of copper, so that it may not be subject to green rust. This is the form recommended by Bergman in his treatise on the application of the blow-pipe to the purposes of the mineralogist, which is contained in the collection of his works. (See Bergman's Opuscula, vol. ii.) For the facility of cleaning, it is in three pieces, which fit in stiff at A and B. Fig. 5 is of tin, that is to say, tinned iron; the small pipe A is of brass, and has two or three caps that fit on stiff; each cap is pierced with a hole of a different diameter; and as the blast issues through this hole, the force of the blast may be varied by changing the cap. This is called Dr Black's blow-pipe. Fig. 6 is of silver; the adjutage, which is of platina, turns on an axis at right angles to the main tube at A, so that it may be made to form different angles with the main tube; the prolongation B serves to receive the condensed vapour of the breath. Fig. 7 is of brass; A is cylindrical, the axis of the cylinder being at right angles

A consists of two pieces, one of which fits air-tight into the other, and may be turned on its axis, so that the pipe of issue may be made to form different angles with the axis of the blow-pipe, as the position of the matter under experiment may require.

Flame consists of vapour in a state of incandescence. Many substances, both of the vegetable, animal, and mineral kingdoms, have the quality of giving out this incandescent vapour. For domestic uses, and for the arts, organized bodies of the vegetable and animal kingdom alone are employed to produce it; such as oils, some of which are solid, others fluid, at the usual temperature of the air, alcohol, ether, wood, and pit-coal. This latter, though found amongst minerals, is composed of organized matter changed and rendered bituminous by a particular process of decomposition. The blow-pipe, by directing the incandescent particles of which the flame consists so as to strike against and surround a small body, produces the effect of heating the body considerably. The flame used with the blow-pipe may either be the flame of an oil or spirit lamp, or of a candle; the flame of the carbonated hydrogen gas proceeding from the distillation of the pit-coal, is also found advantageous for this purpose.

In order to use the blow-pipe, the breath impelled through it is to be directed across the flame of a lamp or candle, applying the orifice from which the air issues a little above the upper end of the wick; and a jet of flame is thus formed, as represented at fig. 8. This jet is made to fall on the body to be heated. The operation may be continued for a considerable length of time; an uninterrupted blast is kept up by the muscular action of the cheeks, whilst the ordinary respiration goes on through the nose; and a little practice is sufficient to enable the operator to succeed. The jet of flame is conoidal, internally blue, and externally yellow. By more or less immersion in this jet of flame the subject of operation receives a greater or less degree of heat, and becomes oxidated in a greater or less degree. If a bead of borax, containing oxide of manganese, be kept fused for some time in the inner flame, the bead becomes colourless; when it is afterwards kept fused in the outer flame, the manganese acquires more oxygen, and the bead becomes of a violet colour. This violet colour may be made to appear more speedily by adding a particle of nitre.

The first who applied the blow-pipe to the analysis of minerals was Swab, counsellor of the college of mines in Sweden in 1738. Its application to the science of mineralogy was afterwards further improved by Cronstedt, Rinnman, Galin, Scheele, and Bergman, and by other men of science since their time.

The blow-pipe is useful to the mineralogist and chemist, as affording a ready method of knowing what the component parts of bodies are. Trials with the blow-pipe are generally made by the chemist in order to know the nature of the constituent parts, before he proceeds to the other steps of dry or humid analysis, which are requisite for ascertaining the quantities of the constituent parts. Then recourse is had to other means than the blow-pipe; for, in order to come at a knowledge of the proportions of the constituent parts, it is necessary that the quantity of each constituent part be large enough to be weighed in a balance, and, for this purpose, the quantity of the substance employed must be larger than what can be managed with the blow-pipe.

In experimental mineralogy with the blow-pipe, the small fragment of the body subjected to trial should not exceed the size of half a peppercorn; if larger, it cannot be sufficiently heated. It is placed in a lenticular cavity, made with a knife, in a piece of well-burnt charcoal of wood, free from cracks, and not too porous, and of the length of four or five inches, so as to be held conveniently in the left hand. Some blow-pipes have been made with a stand, to which they are connected by a ball and socket joint, the stand being fixed to the table by a clamp; and this construction leaves the right hand at liberty. In reducing fragments of metallic ores by the blow-pipe, charcoal should be used as a support, for the charcoal attracts the oxygen from the metallic oxide, and reduces it to a metallic form; and when thus reduced, the metal may be kept fused on the charcoal, which prevents or retards its again attracting oxygen. The charcoal support has likewise the advantage of increasing the heat by its incandescence. For both these reasons, to prevent oxidation, and to increase and reverberate the heat proceeding from the jet of flame, the goldsmith who solders his small work by the blow-pipe attaches his work to a piece of charcoal, by means of wires, in the process of soldering.

When it is required that the fragment of a mineral Support of should be heated without the contact of charcoal, the platina fragment is exposed to the flame in a small spoon of platina, with a wooden handle, the cavity of the spoon being a hemisphere of three tenths of an inch in diameter; or on a thin lamina of platina two or three inches long and half an inch broad, and of the thickness of common writing paper; or it is held by a forceps, three inches long, made of thin platina. Bergman, who published his treatise on the blow-pipe in 1780, before the working of platina had come into use, employed a small gold spoon, as that metal has the quality of remaining pure and uncontaminated, whilst in contact with many of the chemical agents; but platina is preferable; for, besides possessing the quality of resisting the action of many chemical agents, it has likewise the advantage of difficult fusibility. It has now for a good many years been wrought into various instruments both in London and Paris; and when wrought it is sold at the price of about a guinea the ounce, which is one quarter the price of gold. Some platina workers, as Jeanetti of Paris, who was one of the first, form the crude granular platina into masses, by melting it with arsenic, and subsequent heating and forging; others dissolve the crude platina in nitro-muriatic acid, and reduce the nitro-muriate of platina to a metallic state by heat. Platina, however, although infusible alone by the heat of the common blow-pipe, will be dissolved and melted if heated along with some of the metals. Platina supports, therefore, should not be used where they are liable to be in contact with a fused metal. These effects are notable in the case of tin; for when tin is melted in contact with a vessel of platina, the tin enters into a combination with the platina, corroding and rendering it brittle, so that pieces of the platina vessel come off on the application of a small force, and the vessel is thus rendered useless. Platina vessels also become unserviceable by frequent and continued exposure to great heat. Platina crucibles which are much used become brittle, and crack at the edges; and care should be taken to cool these vessels gradually, that they may last as long as possible. A platina vessel, in which sulphuric acid was boiled for a long time, at last became perforated and unserviceable.

Borax (borate of soda) is used along with the fragment Fluxes of mineral in many cases. When exposed to the flame it becomes opaque, swells and ramifies much, in consequence of parting with its water of crystallization; afterwards it fuses into a colourless and transparent bead. It is convenient to use calcined borax, which is borax deprived of its water of crystallization by heat in a crucible: this melts into a bead on the charcoal at once. The solubility of a mineral in borax, with effervescence or without effervescence, and the colour which the mineral communicates to the borax, are the chief distinctive characters obtained. Blow-pipe by treating a mineral with that substance. Phosphate of ammonia is also sometimes used as a flux in the same manner as borax, and carbonate of soda; but both these, especially the latter, have the inconvenience of sinking into the charcoal, which borax is free from.

Mention must be made here of a few of the most prominent phenomena, characteristic of different mineral substances when treated by the blow-pipe. Some minerals are fusible alone, such as garnet and felspar; the last, however, is rather difficult to fuse. Some are infusible, and change colour; bituminous shale loses its black colour, and becomes white; green and dark coloured steatite become white. Some dissolve in borax without effervescence, as agate, quartz, felspar, amiantus, garnet. Some dissolve in borax with effervescence. This is the case with carbonate of lime; it forms with borax a globule transparent whilst in fusion, but in cooling the globule becomes opaque, the lime being no longer held in solution by the borax, in like manner as the watery solutions of certain salts, saturated when hot, deposit a part of the salt on cooling. Some of the metals communicate peculiar colours to borax. Copper, in certain proportions, and at a certain degree of oxidation, gives a brown colour to borax when heated by the blow-pipe; cobalt gives a deep blue tinge; manganese communicates a violet colour; iron tinges borax brown, and, if in greater quantity, black. These colours are produced by the metals in a state of oxide. The smell emitted by some minerals when heated by the blow-pipe is another character serving to distinguish them. That of minerals containing sulphur is the peculiar suffocating smell of sulphureous gas; minerals that contain arsenic emit, when heated, a smell like that of garlic. The nature of some minerals is recognised by the particular form of crystallization which they assume in cooling. This is the case with phosphate of lead, which, after being fused, cools on the charcoal into an opaque white spheroidal polyhedron. Some ores are reduced to a metallic globule with great ease on the charcoal; thus the native sulphuret of lead, called galena, being heated by the blow-pipe, the sulphur is driven off, and the lead remains in its metallic state. A small particle of silver may be melted by the blow-pipe; likewise gold, copper, and, Bergman says, cast-iron. Metallic zinc, when exposed to the flame of the blow-pipe on the charcoal, melts and burns with a bluish-green flame, and becomes covered with oxide, which flies off and floats in the air in light white flocks. Metallic antimony becomes red hot, and melts on the charcoal; and if the operator ceases to blow, a white fume rises, and oxide of antimony forms upon the globule, in whitish crystalline spicules; but if the globule, in a state of fusion, be thrown upon a brick floor, it runs along for a considerable way, rebounding several times, and leaving a trace of white oxide of antimony.

Some substances communicate colour to the flame of the blow-pipe. Muriate of copper, whose crystals are green, communicate a vivid green to the flame; sulphate and nitrate of copper, whose crystals are blue, likewise impart a green colour to the flame when they are exposed to its action. Some of the salts of strontian give a purple tinge to the flame.

The preceding observations relate to the blow-pipe worked by the breath. When it is required to continue the use of the blow-pipe so long that it would be fatiguing if the breath merely were employed, the glass-blower's table, fig. 9, is used. It consists of a double bellows, so fixed as to be worked by the foot, and to impel a current of air through a tin blow-pipe against the flame of a lamp fixed on the table. For the sake of durability, the blow-pipe is sometimes of brass, on which is screwed a nozzle of platina. The blow-pipe may have a stop-cock, as in fig. 9, serving to regulate the blast. The lamp has a cotton wick of nearly an inch in thickness; the wick is kept together by a tin wick-holder, which is soldered to the lamp; and melted tallow fills the lamp, and feeds the wick with fuel. In order to get rid of the smoke, which is in considerable quantity, there may be placed at a convenient distance above the flame a tin funnel ending in a tube, which conveys the smoke out of the room. A convenient method of carrying away the smoke from the glass-blowers' lamp is represented in fig. 13. It consists of a cover of thin sheet copper, which is placed on the table, covering the lamp and nozzle. The fore-part of this cover is open, so as to allow the jet of flame to pass freely. From the upper part of the cover two tubes run upwards for the exit of the smoke; and between these the glass-blower has a view of the object he is at work upon, whilst his eyes are screened from the light of the flame. The two tubes join above in one short tube; and over the open end of this short tube, at a small distance above, is a tube suspended from the ceiling by wires, which conveys the smoke into the chimney of the room. By a handle attached to the cover, the cover with its tubes is removed when it is necessary to trim the wick. The flame of gas from pit-coal may be used instead of a lamp, with a bellows of this kind.

The regularity of the blast in the double bellows is effected by means of a weight pressing on the air contained in the second compartment of the bellows; just in the same way as a stream of air is made to issue regularly from a tube fixed in the mouth of an inflated bladder, when a weight is placed on the bladder. A regular stream of air may also be obtained, by subjecting inclosed air to the pressure of a column of water, mercury, or some other liquid. If a vessel containing air, and open at the mouth, be plunged into the water with the mouth downwards, and if the water on the outside of the vessel rise higher than the surface of the water within the vessel, then the column of water, whose height is the difference of level, exercising its pressure, as all liquids do, in every direction, will act upwards on the inclosed air; the inclosed air, pressed and more condensed than the external air, will escape in a current, by a stop-cock opened on the top of the vessel for its issue; and this issue will continue till the surface of the exterior and interior water come to a level, when the air in the vessel will have the same density as the external air. The force with which the inclosed air is pressed is equal to the weight of a column of water whose height is the difference of levels, and whose base is the surface of water exposed to the inclosed air. The gasometers used by Lavoisier, to afford a stream of oxygen gas and a stream of hydrogen gas, for effecting the composition of water, are constructed upon this principle. An apparatus of the same nature has for many years been employed upon a great scale in different parts of Britain, to regulate the most powerful blast used in the arts,—that for reducing ironstone to the state of cast-iron. In blast-furnaces upon this construction, the blast is raised by means of a large cast-iron cylinder, which acts as a bellows, having a valve in the bottom that opens inwards, and that admits the air during the ascent of the piston; when the piston descends, the valve shuts, and the air is driven into a large parallelopipedal vessel, less in height than in the other dimensions, immersed in water, and having its under surface closed only by the water. In this vessel the air is pressed by the column of water, whose height is the distance between the surfaces of the exterior and interior water; and a pipe of issue, terminating in a nozzle-pipe, conducts the blast to the furnace.

The blow-pipe of the Abbé Melograni of Naples, for the use of the mineralogist, operates by the pressure of water. It is composed of two hollow globes, the upper filled with water, which, by running into the lower, forces the air contained in the lower to issue through a nozzle. This apparatus is described by Mr Greenough, in Nicholson's Journal, vol. ix. p. 25 and 143. It has some inconveniences, and does not appear ever to have come into much use.

The water-pressure apparatus, applied to the blow-pipe, of which a section is given at fig. 10, was contrived by Mr Tilley, an ingenious fancy glass-blower. It consists of a tin box with a partition in it, reaching within half an inch of the bottom; water is poured in, equal in bulk to three fourths of the capacity of the box. The water in the cavity DE is open, and subject to no other pressure but that of the atmosphere, being only covered by the lid of the vessel; the apartment F is closed at top, so as to be air-tight, and the water in it is pressed by the elasticity of the air confined in its upper part. The tube C has its lower extremity always plunged in water, so that when air is blown in through it, the return of the air by that tube is prevented. Before the apparatus is set to work, the surface of the water in both compartments is at the same height, both being pressed by air of the density of the surrounding air; but when air is blown in through C, the air rises through the water to the top of the compartment F; and as the only issue for the air is through the small aperture of the blow-pipe, by which it cannot escape nearly so fast as it is blown in, the air consequently becomes condensed in the upper part of the compartment F; and this condensed air pressing on the water in F more strongly than the atmosphere does on the water in DE, depresses the surface of the water in F, and causes it to rise in DE, which is effected by a portion of the water passing under the partition into the open compartment DE. Thus the pressure exerted by the column of water whose height is the difference of level of the water in DE, and of the water in F, forces the air from the compartment F through the blow-pipe a, which is directed against the flame of a lamp; and this pressure keeps up a constant blast till the water in the two compartments comes nearly to the same height. The degree of condensation of the inclosed air, and the height of the column of water pressing on the condensed air, are measures of each other, when much air is blown in, so as to occasion a considerable degree of condensation. The difference of level resulting is considerable; and the column of water, which is always re-acting with an equal and contrary pressure on the condensed air, causes it to issue with greater velocity from the blow-pipe. When the condensation diminishes, so does the column of water, and the velocity of the issuing stream of air. More air is to be blown in with the mouth through the tube C from time to time, so as to keep the blast regular. Mr Tilley is of opinion that this apparatus produces a more regular stream of air than a double bellows, and it has likewise the advantage that the operator is free from the trouble of moving a pedal. The dimensions of the vessel AA, which is either of tinned iron or of tinned copper, are seventeen inches in height, five inches in width, and nine in breadth; the lid of the vessel opens and shuts on hinges, and supports the tallow lamp B. The bent glass tube a, which terminates in a small hole, is fitted air-tight into a tin tube, which is made conical, and which forms the issue from the top of the compartment F; for this purpose paper is wrapped round the glass tube, and then cotton wick yarn, in a conical form, so that the glass tube thus clothed may fit tight into the socket, and may nevertheless be moved round, that the blast may act properly on the flame. The bent metal tube C is also fixed into its socket in the same manner: its junction with the socket is seen in fig. 10. There is a screen formed of a tin plate sliding vertically in grooves between two upright pieces of tin; the edge of this is seen at S, in fig. 10. It is intended to protect the eyes of the operator from the light of the lamp, whilst, at the same time, he can see the subject of his operation over the top of the screen. This screen is not soldered to the vessel, but is held fast by its foot being placed between the lid of the vessel and the top of the close chamber F. Two rests for supporting the operator's arms project, one from each side of the vessel; upon these the arms are placed when any substance is held to the flame. These rests are wrapped round with woollen list or leather, so as to be more convenient for leaning upon. The whole of the apparatus, including the lamp and case, weighs only three pounds and a half. When it is to be used, the vessel is fixed to a table or bench by means of a leather strap buckled to two loops, which are on the sides of the vessel opposite to each other; and the strap is passed under the table or bench. The long flat cotton wick is preferred by some glass-blowers to the usual round cotton wick. The lamp is filled with tallow, which melts after the lamp has been lighted for some time, and then it burns as freely as oil, and with a less offensive smell. When not in use the tallow becomes solid, and is more conveniently carried about than oil. Hogs' lard also does well for burning in this lamp. Some glass-blowers mix cocoa-nut oil, which is solid at the temperature of the climate of Britain, with hogs' lard, and find it to answer well in the lamp. The lamp is placed within another vessel, marked K, which supports it at a proper height, leaving a space between them, to receive any tallow that may run over the edge of the lamp. A wire bent at the end is convenient for trimming the wick, and forming it into a channel through which the stream of air is to be directed. It is convenient to have several lamps with wicks of different thicknesses, namely, one to hold two flat cottons of about one inch and a quarter broad, another to hold four, a third to hold six, or as much common wick-yarn as is equal to those wicks in bulk, and glass adjutages of different sized apertures to suit the different sized wicks. (See Transactions of the Society for Encouraging Arts, vol. xxxii.)

The eolipile, fig. 11, has been applied to act as a blow-pipe. It is a hollow vessel of brass, sometimes made in form of a small kettle, sometimes in form of a ball of two inches in diameter, with a tube of brass that screws into it. The tube is to be screwed off in order to pour in alcohol by a small funnel, and then the tube being replaced, and heat applied to the bulb, the vapour of the alcohol issues from the small aperture of the tube, and being directed against the flame of a lamp, the flame is driven in a horizontal stream, such as the blow-pipe produces. The instrument has a safety valve, S, to prevent the danger of explosion, which might happen if the nozzle were stopped. The same wick that heats the bulb may serve to furnish the jet of flame, as is the case in the eolipile represented in fig. 11. This instrument has been proposed to be applied to the purposes of the mineralogist; but it does not appear to be either so readily put in action or so efficacious as the common blow-pipe, which is also simpler in its construction, less bulky, and more easily carried about.

Mr Newman, philosophical instrument-maker, of Lisle Street, London, having observed that air condensed in a blow-pipe; cavity required a considerable time to escape through a small aperture made to give it issue, contrived the apparatus represented at fig. 12, which acts as a blow-pipe. This apparatus consists of a strong plate-copper box, perfectly air-tight, three inches in width and height, and four in length; a condensing syringe to force air into the box; and an adjutage with a stop-cock at one end of the box, Blow-pipe by which the issue of the air is regulated. The piston rod of the condensing syringe works through collars of leather in the cap, which has an aperture in the side, and a screw connected with a stop-cock, which may be made to communicate with a jar, bladder, or gasometer, containing oxygen, hydrogen, or other gases. When this communication is made, and the condenser worked, the gas contained in the jar or bladder is thrown into the box, and issues through the adjutage upon the flame of a lamp placed near it. When the apparatus is worked with common air, a few strokes of the piston fills the chamber with compressed air. When the cock of the adjutage is opened, the air issues with great velocity in a small stream, and, when directed on the flame of a lamp, produces a jet of flame as the common blow-pipe does, but with more precision and regularity. The force of the stream of air is easily adjusted by opening more or less the stop-cock of the adjutage; and, when the box has been moderately charged, the stream will continue to issue uniformly for twenty minutes; when the strength of the blast begins to decline, it will be restored by working the syringe. The apparatus is very portable, and not liable to injury. It is made by Mr Newman, the inventor, with a lamp adapted to it, so as to pack up in a box not more than six inches in length and four inches in width and height, enough of space being left for other small articles; others he makes in boxes somewhat larger, so as to contain also a selection of chemical tests. (See Journal of Science, edited by the Royal Institution, No. 1.)

Sir Humphry Davy having discovered that the explosion from oxygen and hydrogen gases would not communicate through very small apertures, Mr Children proposed to him to employ Newman's blow-pipe for effecting a combustion of a mixture of oxygen and hydrogen gas issuing from a small aperture. This Sir Humphry did, and found that the flame produced an intense heat, which instantly fused bodies of a very refractory nature. Dr Clarke, professor of mineralogy at Cambridge, having consulted Sir Humphry on the subject, proceeded to expose a great variety of mineral substances to the flame, for the purpose of observing its effects upon each of them.

The tube of glass through which the mixture of the two gases issues, is cemented on the pipe of issue of Newman's blow-pipe. The tube at first used by Dr Clarke was three inches in length, and the diameter of its cavity 3/8th of an inch. The end of the tube was constantly breaking during the experiments, owing to the sudden changes of temperature, until at last he usually worked with a tube only one inch and three-eighths in length. When the current of gas is feeble, from the gas in the reservoir having come nearly to the same degree of density as the surrounding air, or from the current being suppressed in the beginning of an experiment, then the flame has a retrograde movement, passing up the capillary cavity of the tube about half an inch, and, after splitting the end of the glass tube, the flame goes out of itself; so that, even in this case, there is no danger of explosion. In order to try the effects of an explosion, four pints of a mixture of the two gases were condensed into the chest, which was all that the syringe could force into it. The glass tube was taken off, so that the diameter of the nose-pipe, by which the gas was to issue, was about one eighth of an inch. A burning spirit-lamp was placed at this aperture, and the stop-cock being opened by means of a long string attached to it, the whole gas exploded with a report like that of a cannon; the chest was burst, the stop-cock driven out, and one end of the chest was torn off and thrown against the wall of the room. This shows the danger of using the apparatus with too large an aperture, and the necessity of employing a capillary tube.

When the mixture of the two gases is to be employed in Newman's blow-pipe, the chest is first exhausted of air, and then the gaseous mixture in a bladder, screwed on at Blay N, is to be forced into the chest by the condensing syringe. The proportions of the two gases which Dr Clarke experimented to produce the greatest heat are, two volumes of hydrogen and one of oxygen gas. The intensity of the heat is much greater when the gases are pure; the oxygen procured from manganese does not produce nearly so great a heat as that got from the hyper-oxymuriate of potash. The intensity of the heat may be regulated by allowing the gas to issue in a more or less copious stream, which is done by turning the stop-cock. The heat, Dr Clarke thinks, is greater than that produced by the largest galvanic batteries. Most substances hitherto tried are fused by it, so that it is difficult to find supports for holding the subject of experiment to the flame. The supports employed by Dr Clarke were, charcoal, platina, a piece of tobacco-pipe, black lead. Lime, strontian, and alumine, were fused. The metal of strontian was got, and retained its lustre for some hours. The alkalies were fused and volatilized almost the instant they came in contact with the flame. Rock-crystal fused into a transparent glass full of bubbles. Quartz gave the same result. Opal fused into a pearly white enamel. Flint fused rapidly into a white frothy enamel. Blue sapphire melted into greenish glass balloons, ramified singularly. Foliated talc fused into a greenish glass. Peruvian emerald melted into a transparent and colourless glass, without bubbles. Lapis lazuli fused into transparent glass, with a slight tinge of green. Pure foliated native magnesia, from America, is the substance the most difficult of fusion; it is, however, at last reduced to a white opaque enamel. Agalmatolite of China fuses into a limpid colourless glass. Iceland spar is next in difficulty of fusion to the native magnesia; but it does at last melt into a limpid glass, and, during the process, gives an amethyst-coloured flame, as strontian does; the fusion of pure lime and of all its compounds is attended with a flame of the same colour. Diamond first became opaque, and then was gradually volatilized. Gold, fused along with borax, on a piece of tobacco pipe, was nearly all volatilized. Platina wire, 1/4th of an inch in diameter, melted the instant it was brought into contact with the flame of the gas; the melted platina ran down in drops, and the wire burnt as iron wire does in oxygen gas. Brass wire burnt with a green flame, differing from the green flame that salts of copper give. Copper wire melted rapidly without burning. Iron wire burnt with brilliant scintillation. Plumbago melted into a bead which was attractive by the magnet. Blende or native sulphuret of zinc melted, and metallic zinc appeared in the centre of the melted mass. And metalloid oxide of manganese, crystallized in prisms, was reduced to a metallic state. (See Dr Clarke's Account of his Experiments, in the Journal of Science, edited at the Royal Institution, October 1816.)

Anatomy, a straight hollow tube of brass, of an elongated conical form, six inches in length, and open at both ends. The aperture of the large end is three-tenths of an inch in diameter, that of the smaller end is of the size of a needle's point. It is used for blowing air into the collapsed vessels of the dead subject, in order to know the course of these vessels.

Blowing, in a general sense, denotes an agitation of the air, whether performed with a pair of bellows, the mouth, a tube, or the like.

Blowing, among gardeners, denotes the action of flowers, in opening and displaying their leaves. In this sense, blowing is the same with flowering or blossoming.

The regular blowing season is in the spring, although some plants have other extraordinary times and manners of blowing, as the Glastonbury thorn. Different flowers, also, as the tulip, close every evening, and blow again in the morning. Annual plants blow sooner or later according as their seeds are put in the ground; and hence the curious in gardening sow some every month in summer, to have a constant succession of flowers. The blowing of roses may be retarded by shearing off the buds as they are put forth.

**Blowing of Glass**, one of the methods of forming the various kinds of work in the glass manufacture. It is performed by dipping the point of an iron blow-pipe in the melted glass, and blowing through it with the mouth, according to the dimensions of the glass to be blown. See Glass.

**Blowing of Tin** denotes the melting its ore, after being first burnt to destroy the mastic.

**Blowing Machines**, in the arts and manufactures, and in domestic economy, are instruments for producing a continued current of air, principally for the purpose of facilitating the combustion of fuel. The first idea of such a machine was doubtless derived from the lungs, which we are constantly in the habit of using for the purpose of blowing, but more especially in the simple and useful application of the blow-pipe.

Of these different machines, the common bellows bears the greatest resemblance to the lungs, and was in all probability the first contrivance for artificial blowing. In the first instance, this instrument might be a simple bag, capable of distension by a mechanical force, the air being drawn in and pressed out of the same aperture in the manner of breathing. The first improvement upon this simple form would be to admit the air by a valve opening inwards when the bellows were distended, the blast outwards being from another aperture. This improvement consists in the air being admitted at a wider aperture, which fills the bellows in less time than would be required by the small pipe through which the air is allowed to escape. The blast, in this state of the machine, is not continuous, but in puffs, at intervals of time required for the air to enter the bellows through the valve; the blowing interval being to the filling interval as the areas of the apertures. This irregular blast was for some time remedied by employing two bellows which blew alternately, the blowing on one taking place while the other was filling. The inconvenience, however, was but partially remedied by this contrivance. The invention of what are called double bellows must have been considered a valuable acquisition in the art of blowing. But previous to describing these, it will be necessary to give a description of single bellows above mentioned.

It will be needless, however, to say more than refer the reader to common domestic bellows, which are in every respect the same as the single bellows first used. The leather nailed to the upper and lower boards is prevented from collapsing, when the boards are separated, by a hoop of wood contained within, performing the office of the ribs in the sternum of animals, without which the breathing would not be performed. The lower board contains the valve which admits the air. When the two boards are separated, the air lifts the valve in entering the cavity. When full of air, the closing of the boards causes the air within to close the valve, thus preventing its return in that direction, and compels it to escape at the pipe, the mouth of which is called the nozzle or nose-pipe.

In order to conceive the construction of the double bellows, we have only to take a third board of exactly the same shape as the other two, and connect it with the lower board by a piece of leather similar to that of the single bellows, making two cavities exactly similar, and separated by the lower board of the single bellows, which now becomes the middle board of the double bellows. The third board we shall now call the lower board. This latter has a valve in it exactly similar to the first, which still retains its place in the new construction.

The middle board is now fixed in a horizontal position, the pipe being placed to the fire to be blown. The lower board is held down by a weight, which keeps the lower cavity constantly full of air. The top board has a weight laid upon it, which presses all the air out of the upper cavity through the pipe.

The machinical action by which the blowing is performed is, first, to lift up the lower board. This forces the air from the lower into the upper cavity, the valve in the middle board preventing its return. The weight on the upper board now presses the air with a uniform blast through the pipe. During this time the lower board descends, which fills the lower cavity with air from the atmosphere; and this again rises and gives its contents to the upper cavity, and thence passes through the nose-pipe. Hence we see that that irregular puffing blast which belongs to the single bellows is here confined to the lower board, which supplies air to the upper cavity, while the upper board is constantly pressing uniformly upon the air in it.

Although this is a considerable improvement upon the single bellows, it does not completely obviate the irregularity of the blast. So long as the lower board is not in action, the pressure on the upper board being uniform, the blast is the same. Every time, however, the bottom board rises to force the air into the upper cavity, an extra pressure is given to the air in the upper cavity, and a temporary puff is produced. In the application of bellows to the smith's forge, the continued blast was of less importance than in the blast-furnaces applied to the smelting or refining of ores. The single bellows are at present almost exclusively employed by anchor-smiths and cutlers; while the blacksmith and most others use double bellows, which are doubtless better for all purposes.

In France and other parts of the Continent, bellows have been formed entirely of wood, instead of the flexible bellows. The wooden bellows consist of two boxes, each open on one side, the one being just capable of containing the other; the outer box being placed with the mouth upwards, the other is made to descend into it with the mouth downwards, the latter being capable of moving up and down, while the other remains fixed. In the bottom of the fixed box is a valve like the common bellows, and a pipe on the same level to let out the blast. The change of capacity, by the motion of this box, causes the blast, and with less waste of power than that occasioned by the bending of the leather in the common bellows. This advantage is, however, probably more than compensated by the loss of air from the box not fitting on the sides. See a description of this and some other blowing-machines under Pneumatics.

The common smith's bellows have lately been constructed of a circular form. The boards of these bellows are bellows round, and the movable boards parallel to the horizon and to each other. We have given a view of this construction in Plate CX, figures 4 and 5. A is the blast-pipe, B the movable lower board, C the fixed board, into which the pipe is inserted, and D the upper movable board, on which is placed a weight to regulate the strength of the blast. Motion is given to the lower board by the lever L, and the chain H working on the roller R.

The form of these bellows being cylindrical, the weight required to produce a certain pressure and strength of blast will be easily determined. If the diameter be one foot, the area will be 113-19 inches. The most convenient and pro- Blowing per blast for smiths' bellows is about \( \frac{1}{2} \) lb. upon the inch, or from that to \( \frac{1}{4} \) lb. The upper board, in this case, would require a weight of 56-5 to give a blast equal to half a pound upon an inch. This pressure would give a velocity equal to about 207 feet in a second. If the diameter of the nose-pipe be changed, the number or length of the strokes, or both, must be changed, in order that the pressure and the corresponding density of the blast may remain the same. If the number and length of the strokes be kept up, and the aperture diminished, at the same time that the capacity of the bellows admits not of enlargement, the pressure and density of blast will be increased, although no additional weight be laid on. This frequently happens in the smith's bellows when he makes an increased effort to blow after the upper cavity is full. It is much better, however, not to exert the bellows in this way when a stronger blast is required, but to produce the effect by an additional weight. A very strong blast is found to be injurious to the iron when welding heats are required, and still more so in working steel. It is much better that an increase of air, which is frequently wanted, should be furnished by increasing the aperture, supposing the power to be at the time adequate to keep up the increased supply. Bellows should therefore be so constructed that the pressure may be uniform, and not immediately under the control of the workman. When he wishes to quicken his heat, he should have the means of increasing the aperture by a circular plate turning on an axis at right angles to the length of the pipe, as seen in fig. 9. When in the position \( ab \), the whole area is filled; when in that of \( cd \), the air passes in its full quantity. The index being placed at any intermediate points \( ef \) will let in any proportionate quantity required.

The aperture might be made to change, by the increase of power upon the machine, and thus caused to regulate itself. Several simple contrivances of this kind may be applied by any one skilled in machinery.

These improvements would render the common leather bellows, of the form above given, very useful for smiths. The irregular blast occasioned by their present construction is found to be very injurious to the iron, both as to its quality and economy. This is abundantly shown in the use of some blowing machines lately invented, which have the advantage of a blast that is uniform, and at the same time much softer, being produced by a small pressure.

These blowing machines are also found to answer very well for melting cast iron, the soft blast having less tendency to destroy the carbon, and the quantity of air being compensated by increasing the aperture.

One of these machines is the invention of Mr Street, for which he took out a patent. It consists of a barrel-shaped vessel, from four to five feet in diameter, and of a length more or less proportionate to the work it has to perform.

This cylinder is supported on two bearers by the two ends of its axis, like a barrel churn. The cylinder is divided into two equal parts by a plane in the direction of its length, fitting the two ends and the upper side, watertight, and extending downward to a small distance from the opposite side. This septum is in a perpendicular position when the cylinder is at rest. When this vessel is partly filled with water, and is made to pass through a certain space on its axis, the air which occupies the upper part of the vessel will be compressed on one side by the water, which flows from one side of the septum to the other, and will become in the same degree rarefied on the other, from a contrary cause. If, however, in this situation, a valve be made to open inwards from the atmosphere on the rarefied side, and another to open outwards on the condensed side, two equal and contrary currents will be established, one inwards and the other outwards. On the returning stroke both these valves will shut, and the other two sides will be put in the same situation with the first cavities. If, now, two similar valves to the last be introduced, two similar currents will be produced. If the two valves at which the air escapes from the machine, one on each side of the septum, be made to communicate with one cavity from which a nose-pipe proceeds, while the other two valves communicate with the atmosphere, every stroke will discharge a quantity of air through the nose-pipe from one cavity, and introduce the same volume of air from the atmosphere into the other cavity. These strokes are produced by the oscillating motion of the machine, the limit of its vibrations being about a quarter of the circle, or 90°.

These alternate puffs of air are first propelled into a vessel containing water to regulate the blast. This vessel is divided into two portions by a septum, which passes from the close cover at the top nearly to the bottom. When the air is forced into the cavity, which is close at the top, it expels the water under the septum at the bottom into the open cavity, so as to keep a constant head in the latter, compressing the air in the former. From this air-chest a nose-pipe proceeds to the fire, and the air escapes from it with a uniform velocity so long as the same column of water in the chest is preserved. This description answers to the first machine of the inventor; he has since taken out a second patent, the specification of which is given in the Repository of Arts, vol. xxviii. p. 198. We shall here give a description of this machine, with the patentee's improvements. See Plate CX. figs. 1, 2, and 3.

Fig. 1 is a longitudinal section of this machine. \( AB \) is the cylinder resting upon the axis \( ab \) and \( cd \), which are supported on the uprights \( gg \). The oscillating motion is given to it by a rod working upon the pivot \( p \), the other end of which is connected with a crank of such a length as to cause the cylinder to move through an arch of 90 degrees. The vessel is filled with water to the height \( ee \).

The part CBD (fig. 2) is cut off from the rest of the cylinder by two planes meeting at \( e \), and continuing down to the axis \( x \), so as to work upon its convex surface. These planes extend the whole length of the cylinder, and are then divided transversely into three cavities GHI, as seen in fig. 1. The cavity \( G \) is for the reception of the external air, and is called by the patentee a receiving box. The cavity \( H \) is open to the atmosphere, the periphery of the cylinder being removed in that part. The cavity \( I \) is appropriated to the air which is driven out of the machine, through the valves \( tt \) and \( qq \) (fig. 3), which open alternately on each side. The cavity \( G \) is divided longitudinally in the middle, forming two cavities, \( m \) and \( n \), fig. 2; two valves, \( e \) and \( f \), fig. 1, open into each, one from the end of the cylinder, and the other from the cavity \( H \). Each of the cavities \( m \) and \( n \) communicate with the body of the cylinder by the holes \( hh \) in the dividing planes. The cavity \( I \) has no division, as it receives the air from both sets of exit valves, which escapes at the pipe \( P \).

The axis \( ae \) works within the axis \( ab \) and \( cd \), and is rendered air-tight by a stuffing-box within the latter. This axis will have the effect of remaining at rest while the cylinder is in motion, there being no other force exerted to turn it than the friction of the stuffing-box. The use of this axis is to support and turn a swing valve \( MV \), which is made of rolled iron, strengthened by ribs connected with the axis. This valve is a plane, which would exactly sweep the interior surface of the cylinder without touching it. If the axis \( xe \) be held fast, the valve will retain its perpendicular position, while the cylinder performs its vibrating motion. The water would also remain at rest, with the exception of the motion which its friction and the compression of the air occasions. When the machine moves from D (fig. 3) till the plane DC comes very near to the surface of the water \( w \), the valves \( q q \) open, and a volume of air equal to the space DCS will be expelled through the cavity I (fig. 1), along the pipe P, during the time the valves in the cavity \( m \) (fig. 2) have opened to admit the same volume of atmospheric air on the returning stroke. The point B is carried the contrary way, by which another portion of air opens the valves \( t t \) to pass through the pipe P, while the same volume of air from the atmosphere enters the cavity \( n \), which in its turn is forced through the exit valves \( t t \).

The use of the swing valve MV will now be obvious. If it did not exist, every time the air was compressed on one side the water would be depressed on that side, and the compression of the air would be limited by the increased column of water on the other side. This valve, however, prevents the water from immediately changing its situation, no more escaping from one side of the valve to the other than what can pass between the edges of the valve and the cylinder, which, in the short space of one stroke, can be only a very small quantity. This may be considered as a great improvement upon the first machine, which we have before described. The patentee further intends occasionally to give to this swing valve a contrary motion to that of the cylinder, and thus still more to increase the blast. Or, in the use of a very small blast, the valve may be left at liberty, and used merely to prevent the too great agitation of the water, which in the original machine was considered as an objection. Two of those machines are frequently used together, and worked by cranks, forming an angle of 45° with each other, to make the strong part of the blast of the one to concur with the weak part of the blast of the other.

The part I of the exit pipe PL, must be precisely to the centre of motion. The part L works in a stuffing part, or a ground socket connected with the pipe LN. The latter should communicate with a regulator, which the patentee does not describe, but recommends one of water. This may be a vessel at least of the capacity of the cylinder, inverted in a reservoir of water, and may stand near to the bottom. The pipe N is inserted into the bottom, which is now uppermost. The height of the water in the reservoir must be such as to give the required pressure to the air.

When the air is forced into the inverted vessel by the machinery, the water descends in this, and rises in the reservoir, which now gives a pressure to the contained air equal to the difference of the height of the water in the inverted vessel and the reservoir. The surface of the reservoir should be the greatest possible, in order that it may be raised in the least degree by the water coming from the inverted vessel, which will have the effect of keeping the blast more uniform.

The water regulator is certainly the best for smiths' bellows, for refineries, forges, and perhaps the common melting furnace, but they have been found very objectionable in the blowing of large blast-furnaces. The air in the common blowing engine undergoes a great increase of temperature during its passage through the machine, often as much as 40 or 50 degrees. The heated air has the effect of carrying a greater quantity of water along with it into the furnace, which destroys a larger quantity of carbon than the same bulk of common air, without producing an adequate portion of heat. A great part of the heat of the air is doubtless produced by the friction of the piston of the blowing cylinder, which, in this construction, has a very tight wading. In the blowing machine above described, the water would doubtless be an objection in blast-furnaces, but, as its little friction would not heat the air like the common blowing cylinder used in blast furnaces, the objection would be less formidable. Air must doubtless give out some heat by its decrease of volume, just as it will absorb the heat by rarefaction, as is experienced in exhausting the receiver of an air-pump. The converse of this is equally shown in the little instrument employed to kindle tinder by condensing the air within it.

The heat by the friction of this piston is probably much more than by the condensation of the air; the latter is obviated in the machine above described, and in another blowing machine lately introduced, of which we shall give a description.

This machine, in its general appearance, does not seem to have any advantage over the common blowing cylinder, but in practice it is found superior.

It resembles in some degree the common smith's bellows of the Chinese, which consists of a square wooden trunk, in the form of a parallelopipedon. A board is made to fit pretty nearly its cross section, to which is attached a long rod, by which the board is pushed backwards and forwards like a piston. At one end of the trunk is a valve opening inwards to admit air, and at the same end is a pipe with a valve opening outwards.

The machine above alluded to as having some resemblance to this, is the invention of Mr Vaughan, who has fitted up several of them for foundries, and they are much approved. The writer of this article took a drawing from one of these machines employed to melt cast-iron at the Phoenix Foundery in Sheffield.

Figs. 6 and 7 are two views of the machine. ABCD is a square box formed of pieces of cast-metal, screwed together by hinges. Two of these are placed side by side, as may be seen in the end view, fig. 7. MQ is a piston fitting the square box, which is drawn backward and forward by the rod EF, which works horizontally on the wheels \( w x \) by the spear G, which communicates with the crank of a wheel at a distance.

The piston MQ, which is the most ingenious part of this machine, is enlarged in fig. 8, to render it clearer. The body of the piston is a cast-iron plate about half an inch thick, with a socket in the middle to receive the rod. The diameter of this plate is about one fourth of an inch less than that of the box. Two pieces of wood, \( v n \), are cut diagonally, in order to place the pieces of leather, \( l l \), between them. These leathers, with the wood, are firmly fastened to the plate by bolts, such as \( g h \).

The leathers extend about two inches beyond the wood; and their slight elasticity keeps them in contact with the metallic surface, which is not required to be very smooth. When the piston moves towards the end of the box, to which the leather projects, the leather claps close to the surface, rendering it air-tight, while the leather on the other side of the piston becomes loose, and has no friction. These leathers will be contrarily acted upon when the piston acts the contrary way. The projecting curved pipes HI form a communication between the box where the piston works and the air-chest N. When the piston moves from B to D, the valves F and V open, while L and S are shut. The air contained in the box is now forced through the valve R into the chest N, and from thence along the blast-pipe P.

In the returning stroke, which is the whole length of the box, the valves R, V, and K, are shut, while L and S open. The air is forced through H to N, and then through P.

Two of these work at the same time by two cranks, which cause one to be in full blast at the time the other is returning the stroke; so that, with due management, the four puffs produced by two double strokes may be made to succeed each other at equal intervals, which almost amounts to a steady blast. The inventor recommends four of these boxes all to work together, which would produce eight puffs in the time of one double stroke, which, if divided into equal intervals, would produce a sufficiently uniform blast for any purpose.

When the leathers of the piston are rubbed with black lead, the friction almost amounts to nothing. The leather acts so easy to the surface, and is so flexible, that it may be very easily raised with the fingers. This could not be the case if it were applied in the same way in a cylinder; and this is a sufficient reason for using the square box instead of the cylinder.

This machine makes 70 strokes in one minute; the nose-pipe, where the blast enters the furnace, is 2½ inches in diameter. When the length of stroke is the greatest; at the above speed, it furnishes about 1200 cubic feet per minute.

This machine steers clear of the objection of the water, and, from its small friction, will have less tendency to heat the air. Its original cost is also less than any other machine yet constructed. In the situations where it has been adopted it gives the highest satisfaction. The first construction of Street's bellows, above described, was only fitted for some smiths' fires, where a very soft blast was required. In their improved state they may be employed for most purposes.

All the calculations relative to bellows will be easily made, by the following rules and formula:

First, get the space or capacity formed by one stroke of the machine; call this c, cubic feet.

Then get the number of strokes per minute, which call n.

The area of the nose-pipe, in feet, call a.

The pressure on the air to be discharged, whether by a column of water or by a weight, call p.

v = the velocity with which the air escapes.

r = the resistance, in pounds, which the blast will give.

Then cn = q, the quantity discharged in one minute;

and \( v = \frac{cn}{a} \) in one minute, or \( \frac{cn}{60a} \) for one second.

Then, since the resistance is equal to a column of the fluid of the area a, and twice the height to give the velocity,

\[ \frac{v^2a}{32 \times 14} = p; \] the weight of 14 cubic feet of air being equal to one pound.

The energy of air in blowing fires is as the quantity, and inversely as the space it occupies. For if the same quantity of air be consumed in half the space, the intensity of the heat, or the temperature of that particular place, will be double. Hence it is found that the same quantity of air, by weight, in winter will produce a greater effect on a blast-furnace than in summer, merely from the difference of density. The great difference in produce of iron in the cold and hot seasons of the year is a fact notorious to iron masters.