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with a round hole in the middle, and a handle projectingat one side for lifting it by.

The force of the fire being thus, in great measure, con-centrated upon the crucible in the middle of the fuel ;the crucible is heated, expeditiousiy, and with a littlequantity of fuel, to a very intense degree, while the exte-riour parts of the fuel are of no great heat, and permit theoperator to approach without incommoding him.

In the use of the furnaces hitherto described, the at-tendance of the operator is necessary, both for inspectingthe processes, and for supplying and animating the fuehThere are some operations of a flower kind.; which re-quire a gentle heat to be continued for a length-of time ;which demand little attendance in regard to the operationsthemselves; and in which, of consequence, it is-extremelyconvenient to have the attendance in regard to the fire, asmuch as possible, dispensed with. This end is answeredby the furnace called the athanor; an account of whichis referred to another part of this work, as it Cannot wellbe formed out of black lead pots, and does not fall in withthe simplicity of the present contrivances.

Sundry attempts have been made for keeping up a con-tinued heat, with as little trouble as in the athanor, bythe flame of a lamp; but the common lamp-furnaceshave not answered so well as could be wished. The lampsrequire frequent snuffing, and smoke much; and thefoot, accumulated on the bottom of the vessel-placed overthem, is apt, at times, to fall down and put out theflame. The largeness of the wick-, the irregular supplyof oil from the reservoir by jets, and the oil being sufferedto sink considerably in the lamp, so that the upper partof the wick burns to a coal> appeared to be the principal

causes