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bv heated charcoal fhoukl not be forgotten, par-ticularly the reduction of metallic oxyds, andthe deoxygenation of the fixed acids,; fo that,for example, a fmall heap of minium or lithargeheated red-hot on charcdal by the blow-pipe, isfpeedily reduced to a globule of metallic lead ;the phofphats are partially reduced to phofphu-rets, &c.

For a metallic fupport, platina is in generalby far the bell material. A fmall fpoon ofthis metal is reprefented of the real fize inFig. 74; the {hank of which may be ftuck in acork when held. Fig. 70 is a fmall filver cup,alfo of the real fize, the {hank of which isfixed into a wooden handle. Fufions withborax or alkaline fluxes may be performedin them. Fig. 75 is a fmall forceps latelybrought into ufe, and made entirely of twothin pieces of platina joined by rivets andbent in the manner reprefented. Any fmallhard fubitance may be held by them in theblow-pipe flame for any length of time with-out danger of the points of the forceps melting,and it is also found that this metal is fo muchworfe a conductor of heat than any other, thatthe forceps never get too hot for the nakedfingers to touch at the bend.

In the common way of ufing the blow-pipethere is this inconvenience, that one hand of theoperator is employed in holding the pipe, andthe other, the fupport; fo that he cannot turn,or in any way manage the fubftance heated, nortrim the lamp without Hopping the procefs.Several contrivances have been employed forfupporting one or the other, and giving the ope-rator the free ufe of one or both his hands, fomeof which are complicated enough, efpeciallywhere a candle is ufed, as in this the height ofthe flame is always altering as it burns away.The little apparatus, Fig. 76, is perhaps asconvenient as any, where a lamp is ufed. Thekind of lamp here reprefented is of the fhape ofa flipper, and when employed by the glafs-blowers, the wick is a large fkein of cotton,and the blah is made by double bellows that,are fixed beneath the table and worked by thefoot of the artift, who fits before the lamp, andthus has both his hands and mouth at liberty.The fmoke given out by this kind of lamp isfo much that it is neceflary to have a fmalliron chimney with a flue hanging juft above it.(See the article G/afs, Vol. 1. p. 503.)

Another method of keeping up a continuedftream of air without either the mouth or bel-lows is to fix a blow-pipe tube to the air tubeof a gazometer, PI. V. Fig. 61 St 2. c filled with

common air, and the ftrength of the jet may beincreafedby lefl'eningthe counterpoifing weights.(See the article Gazometer .) The fame appara-tus alfo affords an opportunity of giving in a fmallfpace the higheft poflible heat that combuftioncan procure, by fubftituting oxygen gas to com-mon air in the gazometer. lienee it is of.advantage to have the jet pipes tipped withplatina, for if they are of krais, they are liable,without confiderable care, to melt down by theintenfity of the heat produced, or if of iron,they might readily be burnt. Some of theeffects of this intenfe heat on refraftory bodiesare related under the article Oxygen .

A very ingenious blow-pipe has been in-vented (we believe by Mr. Paul of Geneva,known by his excellent preparations of the ar-tificial mineral waters) which confifts in pallingthe vapour of boiling alcohol through the flameof a lamp, whereby it is kindled, and produces,a very large cone of clear blue flame, perfectlyfree from fmoke, and of fufficient intenfity tomelt fmall quantities of glafs for barometersand thermometers, and for many other ufefulpurpofes. Every part of this apparatus is en-tirely independent of the artift, fo that lie hasboth his hands and mouth at full liberty.

A reprefentation of Mr. Paul’s alcohol blow-pipe with a few alterations is given in PI. VII.Fig. 69. The whole is neatly turned in brafs,and confifts of the following parts.

a is a hollow oval frame about 5 inches inits longeft dimenfion, which fupports the pillard and the two lamps b c, which may burn eitheroil or alcohol, but the latter is the beft. Therim e e flips upon the pillar d as low as the flioul-der of the latter will permit, but the rim may beraifed at pleafure and kept fall by the fcrew r -peg f.The rim fupports the boiler g which is a Angle hol-low piece of thick brafs which will hold aboutan ounce of alcohol, and has four openings,viz. three at top h, i k and one at bottom to re-ceive the tube 0. This latter is long enough toreach to the level of the outfide of the top ofthe boiler, and confequently the alcohol withinthe boiler cannot readily boil over into the tube,and the opening k which correfponds with it,,is clofely {hut by a ferew ftopper, hollowed out"a little beneath, to allow the free paflage ofthe vapour down the tube. Here the vaporizedalcohol is prevented from condenfing at thepoi it 0 by the contiguity of the flame of thelamp b, and as it pafl'es on through the hollowp q into the jet tube r, it is immediately kind-led by the flame of the lamp c, and the unitedflames are compelled fideways with fuch vio-3 T 2

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