Take water made so warm that you can just bear your hand in it, but that has not been boiled; put it under the receiver, and exhaust the air. Bubbles of air will soon be seen to rise, at first very small, but presently become larger, and will be at last so great, and rise with such rapidity, as to give the water the appearance of boiling.

This will continue till the air is let into the receiver, when it will instantly cease.

_Aerial Bubbles._

Take a stone, or any heavy substance, and putting it in a large gla.s.s with water, place it in the receiver. The air being exhausted, the spring of that which is in the pores of the solid body, by expanding the particles, will make them rise on its surface in numberless globules, which resemble the pearly drops of dew on the tops of the gra.s.s. The effect ceases when the air is let into the receiver.

_The floating Stone._

To a piece of cork tie a small stone that will just sink it; and, putting it in a vessel of water, place it under the receiver. Then exhausting the receiver, the bubbles of air will expand from its pores, and, adhering to its surface, will render it, together with the stone, lighter than water, and consequently they will rise to the surface, and float.

_Withered Fruit restored._

Take a shrivelled apple, and, placing it under the receiver, exhaust the air. The apple will immediately be plumped up, and look as fresh as when first gathered: for this reason, that the pressure of the external air being taken off, the air in the apple extends it, so much indeed that it will sometimes burst. If the air be let into the receiver, the apple will be restored to its pristine shrivelled state.

_Vegetable Air-Bubbles._

Put a small branch of the tree with its leaves, or part of a small plant, in a vessel of water, and, placing the vessel in the receiver, exhaust the air.

When the pressure of the external air is taken off, the spring of that contained in the air-vessels of the plant, by expanding the particles, will make them rise from the orifices of all the vessels for a long time together, and produce a most beautiful appearance.

_The Mercurial Wand._

Take a piece of stick, cut it even at each end with a penknife, and immerse it in a vessel of mercury. When the air is pumped out of the receiver, it will at the same time come out of the pores of the wood, through the mercury, as will be visible at each end of the stick. When the air is again let into the receiver, it falls on the surface of the mercury, and forces it into the pores of the wood, to possess the place of the air.

When the rod is taken out, it will be found considerably heavier than before, and that it has changed its colour, being now all over of a bluish hue. If cut transversely, the quicksilver will be seen to glitter in every part of it.

_The Magic Bell._

Fix a small bell to the wire that goes through the top of the receiver. If you shake the wire, the bell will ring while the air is in the receiver; but when the air is drawn off, the sound will by degrees become faint, till at last not the least noise can be heard.

As you let the air in again, the sound returns.

_Feathers heavier than Lead._

At one end of a fine balance, hang a piece of lead, and at the other as many feathers as will poise it; then place the balance in the receiver. As the air is exhausted, the feathers will appear to overweigh the lead, and when all the air is drawn off, the feathers will preponderate, and the lead ascend.

_The self-moving Wheel._

Take a circle of tin, about ten inches in diameter, or of any other size that will go into the receiver, and to its circ.u.mference fix a number of tin vanes, each about an inch square. Let this wheel be placed between two upright pieces on an axis, whose extremities are quite small, so that the wheel may turn in a vertical position with the least possible force. Place the wheel and axis in the receiver, and exhaust the air. Let there be a small pipe with a c.o.c.k; one end of the pipe to be outside the top of the receiver, and the other to come directly over the vanes of the wheel.

When the air is exhausted, turn the c.o.c.k, and a current will rush against the vanes of the wheel, and set it in motion, which will increase, till the receiver is filled with air.

_The Artificial Halo._

Place a candle on one side of the receiver, and let the spectator place himself at a distance from the other side. Directly the air begins to be exhausted, the light of the candle will be refracted in circles of various colours.

_The Mercurial Shower._

Cement a piece of wood into the lower part of the neck of an open receiver, and pour mercury over it. After a few strokes of the pump, the pressure of the air on the mercury will force it through the pores of the wood in the form of a beautiful shower. If you take care that the receiver is clear and free from spots or dust, and it is dry weather, it will appear like a fiery shower, when exhibited in a dark room.

_Magic Fountain._

Take a tall gla.s.s tube, hermetically sealed both at top and bottom, by means of a bra.s.s cap screwed on to a stop-c.o.c.k, and place it on the plate of the pump. When the air is exhausted, turn the c.o.c.k, take the tube off the plate, and plunge it into a basin of mercury or water.

Then the c.o.c.k being again turned, the fluid, by the pressure of the air, will play upon the tube in the form of a beautiful fountain.

_The Exploded Bladder._

Take a gla.s.s pipe open at both ends, to one of which tie fast a wet bladder, and let it dry. Then place it on the plate of the pump. While the air presses the bladder equally on both sides, it will lie even and straight; but as soon as the air is exhausted, it will press inwards, and be quite concave on the upper side. In proportion as the air is exhausted, the bladder will become more stretched; it will soon yield to the inc.u.mbent pressure, and burst with a loud explosion. To make this experiment more easy, one part of the bladder should be sc.r.a.ped with a knife, and some of its external fibres taken off.

_The Cemented Bladder._

Tie the neck of the bladder to a stop-c.o.c.k, which is to be screwed to the plate of the pump, and the air exhausted from the bladder; then turn the stop-c.o.c.k, to prevent the re-entrance of the air, and unscrew the whole from the pump. The bladder will be transformed into two flat skins, so closely applied together, that the strongest man cannot raise them half an inch from each other; for an ordinary-sized bladder, of six inches across the widest part, will have one side pressed upon the other with a force equal to 396 pounds' weight.

_Cork heavier than Lead._

Let a large piece of cork be pendent from one end of a balance beam, and a small piece of lead from the other; the lead should rather preponderate. If this apparatus be placed under a receiver on the pump, you will find that when the air is exhausted, the lead, which seemed the heaviest body, will ascend, and the cork outweigh the lead.

Restore the air, and the effect will cease. This phenomenon is only on account of the difference of the size in the two objects. The lead, which owes its heaviness to the operation of the air, yields to a lighter because a larger substance when deprived of its a.s.sistance.

_The animated Bacchus._

Construct a figure of Bacchus, seated on a cask; let his belly be formed by a bladder, and let a tube proceed from his mouth to the cask. Fill this tube with coloured water or wine, then place the whole under the receiver. Exhaust the air, and the liquor will be thrown up into his mouth. While he is drinking, his belly will expand.

_The Artificial Balloon._

Take a bladder containing only a small quant.i.ty of air, and a piece of lead to it, sufficient to sink it, if immersed in water. Put this apparatus into a jar of water, and place the whole under a receiver.

Then exhaust the air, and the bladder will expand, become a balloon lighter than the fluid in which it floats, and ascend, carrying the weight with it.

_Curious Experiments with a Viper._

Many natural philosophers, in their eagerness to display the powers of science, have overlooked one of the first duties of life, humanity; and, with this view, have tortured and killed many harmless animals, to exemplify the amazing effects of the air-pump. We, however, will not stain the pages of this little work by recommending any such species of cruelty, which in many instances can merely gratify curiosity; but as our readers might like to read the effect on animals, we extract from the learned Boyle an account of his experiment with a viper.

He took a newly-caught viper, and, shutting it up in a small receiver, extracted the air. At first, upon the air being drawn away, the viper began to swell; a short time after it gasped and opened its jaws; it then resumed its former lankness, and began to move up and down within the receiver, as if to seek for air. After a while, it foamed a little, leaving the foam sticking to the inside of the gla.s.s; soon after, the body and neck became prodigiously swelled, and a blister appeared on its back. Within an hour and a half from the time the receiver was exhausted, the distended viper moved, being yet alive, though its jaws remained quite stretched; its black tongue reached beyond the mouth, which had also become black in the inside: in this situation it continued for three hours; but on the air being re-admitted, the viper's mouth was presently closed, and soon after opened again; and these motions continued some time, as if there were still some remains of life.