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of the pipe itself is hollowed so as to perform the sameoffice : at the top it is twelve inches and a fifth in dia-meter (Engliffi measure) from thence it grows narrowerto the depth of nearly thirty-four inches, where its widthis only about three inches and three quarters : immedi-ately below this part, called the choak, its cavity widensto nearly eight inches and a half, and this width it pre-serves throughout the rest of its length. Under the choakare ten air holes, six of which are in one horizontalplane, at equal distances from one another, and the restabout three inches and three quarters lower down : allthe holes are cylindrical, near two inches in diameter*and cut at such an obliquity, that the orifice of the upperones is on the inside of the pipe eight inches, and on theoutside only five inches, below the choak.

The tub or air vessel, which receives the lower end ofthe pipe, is five feet and a half, or a little more, in depth,and nearly as much in width : the pipe enters into itabout seventeen inches : about the middle of its height isa flat stone or iron plate, supported by cross bars of wood.The air passes off, as already mentioned, through a pipeinserted into the upper part of the tub, and the waterthrough a hole at the bottom : on the outside of thishole is fixed a wooden frame, with an upright slider, bywhich the aperture for letting out the water may be oc-casionally increased or diminished. The blast is regu-lated, and the air suffered to escape when it is not wanted,by a hole in the blowing pipe, to which is fitted a valveor a stopper.

One of these machines is said to be sufficient for theforge or iron finery, and two or three for the furnace inwhich the iron ore is run down.

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