BLOW-PIPE, 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-pinching, 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 soldering; it is of brass. Fig. 2 is Dr Wollaston’s blowpipe, 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 Berg-mani 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 [7:4:713]to the axis of the blow-pipe. 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 pitcoal, 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 Cronsted, Rinman, Gahn, 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.

ŗ 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 arc 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 should be heated without the contact of charcoal, the 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 uncontaini-nated, 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 Jean-etti 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 blowpipe, 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 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 ιι 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 [7:4:714]by treating a minèraI 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 galaena, 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 spiculae; 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 blowpipe 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 nosepipe, 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.]
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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 Nicholsons 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 airtight, 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. xxxi.)

The colipile, fig. 11, has been applied to act as a blowpipe. 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 colipile 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 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 pne end of the box, [7:4:716]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 N 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 7- l (jth 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 N, is to be forced into the chest by the condensing syringe. The proportions of the two gases which Dr Clarke found 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 potass. 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, ⅛th 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 bril hant scintillation. Plumbago melted into a bead which was attractable 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.) (ß. B.)

Blow-Pipe, in 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.