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If a pot is to be fitted up on purpose for a blast fur-nace, no other aperture is required than a round one inthe side for the nose of the bellows to enter, the fuelbeing here thrown in at the top : all other apertures need-lessly weaken the furnace. The pot should be of thelargest size : if a cover or dome, or an additional partfor enlarging its capacity, is wanted, another pot of thelame size, with a portion of its lower narrow part sawedoff, makes a very convenient one ; and this narrow part,as we shall see. hereafter, will be of use for anotherpurpose. A round plate or slip, sawed from the solid partos the bottom, serves very commodiously both for a grate,and for a support to the crucible : eight or nine holes,about three quarters of an inch in diameter, are boredround the outer part of the plate, for the transmission ofthe air forced in by the bellows ; and four or five smallcrucibles may be placed together in the middle : theholes are made to widen downwards, to prevent theirbeing choaked up by pieces of the fuel.

The bellows I have chiefly employed is the organbellows j with this variation in its structure, that theupper board, instead of rising obliquely on hinges at onefide, rises equally on all sides, and continues always hori-zontal. On account of the flexibility or pliableness ofthe leather of this kind of bellows, it is not only movedfar easier than the common ones, whose leathers are stiff,but is likewise free from their inconvenience of resistingunequally according to the greater or less extension cfthe folds. The board is pressed down, and the air forcedout, by a weight on the top : in the common bellowsthis weight, pressing on an inclined plane, whole incli-nation is continually changing, has its force changing in

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