is very strong, and bent into two cranks of nine inches radius, at
right angles to each other, is applied the propelling power by means
of pistons from two horizontal cylinders. By this contrivance, and a
peculiar mode of admitting the steam to the cylinders, Mr. Gurney has
very ingeniously avoided that cumbersome appendage to steam-engines,
the fly-wheel, and preserves uniformity of action by constantly having
one cylinder on full pressure, whilst the other is on the reduced
expansive. The dead points--that is, those in which a piston has no
effect from being in the same right line with its crank,--are also
cleared by the same means. For as the cranks are at right angles, when
one piston is at a dead point, the other has a position of maximum
effect, and is then urged by full steam power; but no sooner has the
former passed the dead point, than an expansion valve opens on it with
full steam, and closes on the latter. Firmly fixed to the extremities
of the axle, and at right angles to it, are the two 'carriers'--(two
strong irons extending each way to the felloes of the wheels.) These
irons may be bolted to the felloes of the wheels or not, or to the
felloes of one wheel only. Thus the power applied to the axle is
carried at once to the parts of the wheels of least stress--the
circumferences. By this artifice the wheels are required to be of no
greater strength and weight than ordinary carriage-wheels; and, like
them, they turn freely and independently on the axle; but one or
both may be secured as part and parcel of the axle, as circumstances
require. The carriage is consequently propelled by the friction or
hold which either or both hind-wheels, according as the power is
applied to them jointly or separately, have on the ground. Beneath
the hind part drop two irons, with flat feet, called 'shoe-drags.' A
well-contrived apparatus, with a spindle passing up through a hollow
cylinder, to which the guiding handle is affixed, enables the director
to force one or both drags tight on the road, so as to retard the