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.
THE PNEUMATIC PHIAL.
Provide a phial one-fourth filled with any coloured water, and with a glass tube passing through the cork, or cemented into the neck of the phial, so as to be air-tight; the tube may reach to within a quarter of an inch of the bottom of the phial, so as to dip below the surface of the liquid. Hold this little instrument before the fire, or plunge it into hot water, when the air that is in the phial will expand, and force up the coloured liquor into the tube.
RESIN BUBBLES.
Dip the bowl of a tobacco-pipe into melted resin, hold the pipe in a vertical position, and blow through it; when bubbles of various sizes will be formed, of a brilliant silvery hue, and in a variety of colours.
MOISTURE OF THE ATMOSPHERE.
Moisture is always present in the air, even when it is driest. To prove this, press a piece of sheet copper into the form of a cup; place on it a piece of phosphorus, thoroughly dried between blotting-paper; put the cup on a dry plate, and beside it a small piece of quick-lime; turn over it a glass tumbler, and leave it for ten minutes, that the lime may remove all moisture from the included air; take off the tumbler, touch the phosphorus with a hot wire, and instantly replace the glass; when a dry solid will be formed, resembling snow. As soon as the flame is extinct, examine the plate; when the solid will, in a very short time, attract so much water from the air, that it will pass into small drops of liquid.