Having seen that round iron is produced by the junction of two semicircular grooves in the opposite rollers, the reader will readily perceive, without the aid of a figure, that " half-round iron," (that is, semicircular in its transverse section,) will be produced by having only one roller with a semicircular groove, and the opposite roller with no groove at all; and that, by making the groove of less depth, that is, of an elliptical curve, a semi-elliptical, or " half-oval" iron bar will be formed; also that by the junction of two semi-elliptical grooves, "oval iron" will be the result. The two last-mentioned sorts are extensively used by coach smiths; also for the tops of fenders, wire-guards, and such like. It will likewise be evident to the reader, that as square iron is made by two angular grooves, one of such grooves opposed to a plain roller will produce triangular, or "three-square iron;" that as flat bars are made by grooves of this form - , it will be only necessary to make the opposite groove deep and narrow, thus l, and let the latter groove come next to one end of the former, to produce L or "angle-iron." This angle-iron, though of recent introduction, is, on account of its very great utility in making framing, cases, boilers, and a thousand other things, a great favourite with all kinds of smiths, as it enables them to execute superior work with much less labour.

Seeing how the angle-iron is made, it will be readily understood that, by placing this I groove so as to come in the middle of this - groove in the opposite roll, that " T iron " will thereby be rolled; and this brings us to a clear understanding how "railway-iron" is made, as the form is usually but a slight modification of the T, by a little rounding of some of the parts; and by obvious combinations of the foregoing, it will be seen how "iron mouldings," of an infinite variety, may be produced by a pair of rolls, and with far more facility and dispatch than a joiner can make them of wood with his moulding planes.