1

Of the Air~Pumf

lettirtg the air into the receiver again, it will overpower the air in thebladder, and press its fides almost dose together.

15. If the bladder so tied up be put into a wooden box, and have20 or 30 pounds weight of lead put upon it in the box, and the boxbe covered with a dose receiver; upon exhaufting the air out of thereceiver, that air which is confined in the bladder will expand itselfso, as to raise up all the lead by the force of its spring.

16. Take the glass ball mentioned in the fifth experiment, which Fig. 7.was lest füll of water all but a small bubble of air at top, and having

set it with its neck downward into the empty phial a <2, and coveredit with a dose receiver, exhaust the air out of the receiver, and thesmall bubble of air in the top of the ball will expand itself, so as taforce all the water out of the ball into the phial.

17. Screw the pipe A B into the pump-plate, place the tall receiver Fig. ,i.G H upon the plate c d, as in the twelfth experiment, and exhaust

the air out of the receiver; then, turn the cock e to keep out the air,unscrew the pipe from the pump, and screw it into the mouth of thecopper vessel CG (Fig. 15.) the vessel having first been about halffilled with water. Then turn the cock e (Fig. 11.) and the spring ofthe air which is confined in the copper vessel will force the water upthrough the pipe AB in a jet into the exhausted receiver, as stronglyas it did by its pressure on the surface of the water in a bason, in thetwelfth experiment.

18. If a fowl, a cat, rat, mouse, or bird, be put under a receiver*and the air be exhausted, the animal will be at first oppressed as witha great weight, then grow convulsed, and at last expire in all theagonies of a most bitter and cruel death. But as this experiment is toofhocking to every spectator who has the least degree of humanity, wesubstitute a machine called the lungs-glass in place of the animal jwhich, by a bladder within it, fhews how the lungs of animals arecontracted into a small compass when the air is taken out of them.

19. If a butterfly be sufpended in a receiver, by a fine thread tiedto one of its horns, it will fly about in the receiver, as long as the re-ceiver continues füll of air; but if the air be exhausted, though theanimal will not die, and will continue to flutter its wings, it cannotremove itself from the place where it hangs in the middle of the re-ceiver, until the air be let in again, and then the animal will fly aboutas before.

20. Pour some quicksilver into the small bottle A, and screw the Fig. iz,brass collar c of the tube B C into the brass neck b of the bottle, and

the lower end of the tube will be immerscd into the quicksilver, so2 that