19.  Propellers, which, as the carriage ascends a hill, are set in motion, and move like the hind legs of a horse, catching the ground, and then forcing the machine forward, increasing the rapidity of its motion, and assisting the steam power.

20.  The Drag, which is applied to increase the friction on the wheel in going down a hill.  This is also assisted by diminishing the pressure of the steam—­or, if necessary, inverting the motion of the wheels.

21.  The Clutch, by which the wheel is sent round.

22.  The Safety Valve, which regulates the proper pressure of the steam in the pipe.

23.  The Orifice for filling the Tank.  This is done by means of a flexible hose and a funnel, and occupies but a few seconds.

* * * * *

Mr. Goldsworthy Gurney, whose name is already familiar to most of our readers, after a variety of experiments, during the last two years, has completed a steam carriage on a new principle; or, as a wag said the other day, he has at length brought his plan to bear.  We have, accordingly, procured a drawing of this extraordinary invention, which we shall proceed to describe generally, since the letters, introduced in the annexed Engraving, with the accompanying references, will enable our readers to enter into the details of the machinery:—­First, as to its safety, upon which point the public are most sceptical.  In the present invention, it is stated, that, even from the bursting of the boiler, there is not the most distant chance of mischief to the passengers.  This boiler is tubular, constructed upon philosophical principles, and upon a plan totally distinct from any thing previously in use.  Instead of being, as in ordinary cases, a large vessel closed on all sides, with the exception of the valves and steam conductors, which a high pressure or accidental defect may burst, it is composed of a succession of welded iron pipes, perhaps forty in number, screwed together in the manner of the common gas-pipes, at given distances, extending in a direct line, and in a row, at equal distances from a small reservoir of water, to the distance of about a yard and a half, and then curving over in a semi-circle of about half a yard in diameter, returning in parallel lines to the pipes beneath, to a reservoir above, thus forming a sort of inverted horse-shoe.  This horse-shoe of pipes, in fact, forms the boiler, and the space between is the furnace; the whole being enclosed with sheet-iron.  The advantage of this arrangement is obvious; for, while more than a sufficient quantity of steam is generated for the purposes requited, the only possible accident that could happen would be, the bursting of one of these barrels, and a temporary diminution of the steam-power of one-fortieth part.  The effects of the accident could, of course, only be felt within its own enclosure; and the Engineer could, in ten minutes, repair the injury, by extracting the wounded barrel, and plugging up the holes at each end; but the fact is, that such are the proofs to which these barrels are subjected, before they are used, by the application of a steam-pressure five hundred times more than can ever be required, that the accident, trifling as it is, is scarcely possible.