Ground Wheels.
13. Ground Wheels.
These are of very simple contrivance. Provide two light wheels, in diameter from two to three or four feet: they must be fixed firmly to a square axle-tree, or in such manner that they cannot revolve on it; the axle may be about three feet in length. Then on the middle of this axle is to be firmly fixed a fire-wheel, which must be so much less in diameter, that when the cases are attached to it, it may be quite clear of the ground; care must be taken that this middle wheel be fixed at right-angles from the axle, or it will not keep in a straight direction when set in motion. Now the first case being fired, it is evident that motion will be given to the fire-wheel, which being fixed firmly to the axle of the others, the consequence which follows is, that absolute[16] motion will be given to the whole apparatus; which, if placed on level ground, will proceed to a distance proportionate to the number and strength of the cases employed.
By attaching a second set of cases, so arranged as to take fire when the first set are consumed, the wheel (running upon level ground) will return to the same place from which it received its primary impulse.
This kind of wheels, when constructed with care, affords a very pleasing recreation. It may be readily seen, that many other ornamental pieces of less magnitude may be attached to the same axle:—a good level school ground is favourable for the exhibition of this article.