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neck and body, it forms two fimilar glaffes ex-tremely convenient for many fmall operations,and in which the fplit part of the neck fervesboth as a fpout and handle. The greateft incon-venience attending thefe veffels made out offlalk, is their exceffive thinnefs at the middle,fo that they are liable to fplit by the leaftblow, and when full of liquor they can hardlybe taken up without danger of being broken bythe prelfure of the hand.

FORGE. See Furnace.

FUEL. See Furnace.

FUNNEL. The common funnel needs nodefcription. It may be made either of glafs orpewter, or tinned iron, or earthen-ware.

The ribbed funnel , PI. I. Fig. 7. is better forfupporting large paper filters than the plainones; for in the latter cafe, the wet paper ad-heres fo clofely to the fmooth glafs as mollmaterially to prevent the paffage of the liquorthrough; whereas the ribbed funnels afford asmany channels through the whole length of thepaper, by which the fluid is drawn down to thebottom. A plain funnel may be made equalor fuperior to the ribbed, by arranging in a per-pendicular diredlion at equal diftances, a num-ber of ftraws, or pieces of thin glafs rod,to form an uneven furface, over which the paperfilter is to be laid, and thus to prevent its ad-hering to the fide.

It is ufeful to have in a laboratory a fmallglafs funnel with a very long narrow neck,able to pafs down the whole neck of a retort,by which liquors may be poured in, without anypart of them wetting the neck of the retort.

FUNNEL SEPARATORY. The fepara-tory funnel, PL II. Fig. 40. is intended for thefeparation of liquids of different fpecific gravity(as oil and water) by allowing the heavieft onlyto drop out of the bottom of the veflel. Thefunnel is firft flopped at the bottom and thenfilled with the mixed liquors. When they haveflood at reft till the heavieft has entirely fub-fided into the narrow part below, the cork atbottom is taken out, and when the Hopper aboveis a little loofened the heavier liquor flows out.This veffel is ufed particularly in feparatingeffen'tial oils from the water which is neceffarilyentangled with them when colledled from the„water diftilled from the plants that yield them.

’ Some of thefe are lighter than water, others hea-vier, and they are both feparated with equal eafe.

FURNACE.

As heat is one of the great agents in chemi-cal proceffes, the conffru&ion of the apparatusthrough and in which heat is applied mull be

of the firft confequence, and accordingly a vaftquantity of pains and ingenuity has been be-llowed on the fubjecl of furnaces. To deferibeevery one that has been invented for general orparticular purpofes would far exceed our limits,we fhall therefore only mention fome of thofewhich are the moll commonly employed in thelaboratory. The furnaces required for workingores and metals in the large way, for makinglime, bricks, pottery, glafs, &c. are foreignfrom our prefent fubjecl, and moft of themhave been noticed under thefe refpedtivearticles as fully as is confiftent with our generalplan.

The furnace which is the moft familiar to usis the Common Grate. This is an iron furnaceof various fhape cut down in front and the fuelkept in only by bars, in order to throw the heatout into the room. The utmoft heat of a com-mon parlour Hove fupplied with coals is barelyfufficient to melt thin plate filver, for a piece offilver money will not readily melt in it unlefs itburns very ftrongly. But a very large numberof the operations in chemiftry are performedin a temperature not exceeding full rednefs, andfor many of thefe the common grate is amplyfufficient. The flat iron fides or cheeks willalfo furnifh an inferior heat, on which evapo-rating and digefting veffels may be fet. Thecommon grate however has two difadvantages,one, that the opennefs of the front caufes theefcape of a great part of the heat, and incom-modes the chemill in approaching it, and theother that coal is a very unfteady variable fuelgiving much blaze and ftnoke, and requiringfrequent ftirring.

Before we deferibe the proper chemical fur-naces, we may fhortly Hate what mull be theirobject and conftru£tion.

The fimpleft air-furnace that we can con-ceive is a cylindrical or conical earthen pot,open at top and with a grate fixed withina few inches from the bottom, and a prettylarge opening juft beneath it, in order toallow of the draught of air through the fueland for the aflres to be cleared out. Thisdraught-hole beneath the grate, of whateverform it be, is always called the ajh-hole or ajh-pit. If furnifhed with a Hopper, the draughtof air and ctmfequent intenfity of the fire mhybe regulated. The fuel is thrown in and thecrucibles to be heated are introduced down thelarge opening at top. A cylindrical earthenpot thus conllrufted has already leveral advan-tages over the common grate of the fame capa-city ; for the fides being entirely doled, the