[Illustration: Fig. 1.]
[Illustration: Fig. 2.]
To construct this pretty little pneumatic toy, take a square piece of
stiff card, or sheet copper or brass, about two and a half or three
inches in diameter, and cut it out spirally, so as to resemble a snake,
as in the engraving (fig. 1.). Then paint the body on each side of the
card the colours of a snake; take it by the two ends, and draw out the
spiral till the distance from head to tail is six or seven inches, as
in fig. 2. Next, provide a slender piece of wood on a stand, and fix
a sharp needle at its summit; push the rod up through the spiral, and
let the end of the spiral rest upon the summit of the needle. Now place
the apparatus as nearly as possible to the edge of the mantel-shelf
above the fire, and the snake will begin to revolve in the direction
of its head; and, if the fire be strong, or the current of heated air
which ascends from it is made powerful, by two or three persons coming
near it, so as to concentrate the current, the snake will revolve
very rapidly. The rod _a_, _b_, should be painted, so as to resemble
a tree, which the snake will appear to climb; or, the snake may be
suspended by a thread from the ceiling, over the current of air from a
lamp. Two snakes may be made to turn round in opposite directions, by
merely drawing out the spiral of one from the upper side, and of the
other from the under side of the figure, and fixing them, of course, on
separate rods.