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like manner, and thus produces an irregular blast, and anunsteady heat : in ours, the weight, acting always per-pendicularly, has always an equal power, and the air ispropelled in one unvaried current. The fame advantagemay be procured also to bellows of the common construc-tion, by an alteration only in the disposition of the weight;which, instead of being placed on the top, should be hungat the extremity, upon an arc, furniffied with a groovefor receiving the cord, and whose center is the point onwhich the board moves : the weight being thus made toact always in a perpendicular direction, and at an equaldistance from the center of motion, an equality of itspower is effectually secured. By these means, the heat iskept up uniform ; and may be easily increased at pleasure,by increasing the weights, to the greatest degree that canbe excited in furnaces ; in which intention it will be ofadvantage to have the nozzle of the bellows wider thanusual, that the air may be the more freely dischargedfrom it. The bellows is of no incumbrance in theelaboratory, being inclosed in a wooden case, whose coverdoes the office of a common table : to the nozzle, whichjust comes through the cross bar at the bottom of thetable, is occasionally fitted a pipe reaching to thefurnace.

The bellows thus disposed serves likewise for impellingand concentrating the flame .of a lamp upon bodies ex-posed to it. For this purpose, an upright tin pipe isfitted on the nozzle by a short elbow at its lower end ;and at its upper end is a moveable elbow, into which isinserted a lesser pipe, having a very small aperture in itsextremity : this aperture being applied to the flame of alamp placed upon the table, and the pipe blown through ;the flame lengthens in the direction of the blast, and

D 2 converges