ent to thus divide the labour than to endeavour to form the
wheel of fewer component parts. The wheel is now taken to the lathe,
and a portion is cut away from its edge, till a groove is left so as
to dovetail into the tyre.

The tyres, which are of steel, are not made here; they come ready to
be placed upon the wheel, and some care has to be taken in moving
them, for, although several inches in thickness and of enormous
strength, it has occasionally happened that a sudden jar from other
solid bodies has fractured them. One outer edge of the tyre is
prolonged, so to say, and forms the projecting flange which holds
the rails and prevents the carriage from running off the road. So
important a part requires the best metal and the most careful
manufacture, and accordingly no trouble or expense is spared to
secure suitable tyres. One of the inner edges of the tyre, on the
opposite side to the flange, is grooved, and this groove is intended
to receive the edge of the wheel itself; they dovetail together
here. The tyre is now made hot, and the result of that heating is an
expansion of the metal, so that the circle of the tyre becomes
larger. The wheel is then driven into the tyre, which fits round it
like a band. As it grows cool the steel tyre clasps the iron wheel
with enormous force, and the softer metal is driven into the groove
of the steel. But this is not all. The wheel is turned over, and the
iron wheel is seen to be some little distance sunk, as it were,
beneath the surface of the tyre. Immediately on a level with the
iron wheel there runs round the steel tyre another deeper groove.
The wheel is again heated--not to redness, for the steel will not
bear blows if too hot--and when the tyre is sufficiently warm, a
long, thin strip of iron is driven into this groove, and so shuts
the iron wheel into the tyre as with a continuous wedge. Yet another
process has to follow--yet another safeguard against accident. The
tyre, once more heated, is attacked with the blows of three heavy
sledge-hammers, wielded by as many stalwart smiths, and its inner
edge, by their well-directed blows, bent down over the narrow band
of iron, or continuous wedge, so that this wedge is closed in by
what may be called a continuous rivet. The wheel is now complete, so
far as its body is concerned, and to look at, it seems very nearly
impossible that any wear or tear, or jar or accident, could
disconnect its parts--all welded, overlapped, dovetailed