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The gradual succession of bellows to this precariousand insufficient way of supplying air, and the gradualimprovements made in the structure and manner of work-ing of the bellows, cannot perhaps be traced. It appears,that at some of our iron furnaces and others, the bellowswere formerly moved by a handle as those of the smith’sforge, or by the pressure of the foot upon a treadle, orby other means requiring the strength of men : and that,fince the force of water has been called in aid to movethem, the quantity of ore run down has not only beenfar greater, but the separation of the metal more complete;insomuch, that great part of the iron now prepared atsome considerable works, particularly in the county ofGloucester, is no other than what had been formerlyleft in the fags or cinders for want of sufficient forceof air.

The bellows used at our furnaces are composed of twoboards joined by leather, nearly in the fame manner as thecommon bellows. A cheaper kind of bellows, made en-tirely of woood, was introduced at the furnaces of theHartz forrest in Germany, according to Schluter, aboutthe year 1620, and has since been received in Swedenand some parts of France. It consists of two long boxes,of the fame figure with the smiths bellows, one of whichdrops over the other, and is of such depth, that whenraised up on a hinge as high as it is intended to be, it nowhere comes entirely off: the air enters by a valve as inother bellows, and is forced out by pressing down theupper box : along the edges of the lower or inner boxare placed laths, which stide horizontally in grooves, andto which are fitted springs capable of pressing them aninch or two beyond the box, so as to form a ledge, ofvariable width, which always accommodates itself t-o the

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