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in the fire : thus it uniformly fills the interstices, andjoins the pots sufficiently together, yet not so firmly butthat upon occasion they may be easily separated again.

The fuel, for producing or continuing vehement sire,should be the most ponderous and compact kind of char-coal, as that of the oak or beech, free from bark, andin pieces about the size of hens eggs. It should be keptready lighted, for continual supplies, in another vessel,such as the open furnace formerly described ; and freshquantities of the burning charcoal thrown in every sevenor eight minutes, or in proportion to the quickness ofthe consumption, that the crucible may always continuecovered. Where a dome is used, a supply of lighted fuel iscommodioufiy obtained by means of an iron plate, turnedup at the sides into a kind of square trough, and hookedon the fire-place door : the trough being filled withcharcoal, the inner part os the coals is kindled by thevicinity of the fire, and this is moved into the furnaceby successively pushing forward the unsighted part. Somehave imagined that the supplying of fuel previously madered hot could affect only those kinds of operations, inwhich the vessel is set over the sire, and the fresh fuelinterposed between the fire and its bottom ; and that thispractice could be of no advantage in the melting furnace,where the crucible is placed in the middle of the fire,But though, in this last circumstance, the previous kind-ling of the fuel has much less influence than in theother, it is by no means to be disregarded : the upperpart of the crucible may sometimes be nearly bare, andsome of the pieces thrown in may drop down throughvacuities about the sides ; in which cafes it is obvious,that the injection of cold or unsighted coals, must neces-sarily, for a time, diminish the heat about the vessel, andlikewise endanger its cracking.

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