142 PNEUMATICS. 



10. Screw the pipe A B (Fig. 9.) into the pump- 

 plate, place the tall receiver G H upon the plate 

 e d, as before, and exhaust the air out of the re- 

 ceiver ; then turn the cock e to keep out the air, 

 unscrew the pipe from the pump, and screw it into 

 the mouth of the copper .vessel C (Fig. 10.), the 

 vessel having been first about half filled with 

 water. Then open the cock e, and the spring of 

 the air which is confined in the copper vessel will 

 force the water up through the pipe A B in a jet 

 into the exhausted receiver, as strongly as it did 

 by its pressure on the surface of the water. 



11. If a rat, mouse, or bird, be put under a re- 

 ceiver, and the air exhausted, the animal will be at 

 first oppressed as with a great weight, then grow 

 convulsed, and at last expire in agonies. But as this 

 experiment is too shocking to most spectators, it is 

 common to substitute a machine called the lungs 

 glass in place of the animal. 



12. If a butterfly be suspended in a receiver, by 

 a fine thread tied to one of its horns, it will fly 

 about in the receiver as long as it continues full of 

 air j but if the air be exhausted, though the animal 

 will not die, and will continue to flutter its wings, 

 it cannot remove itself from the place where it 

 hangs in the middle of the receiver, until the air 

 be let in again, and then the animal will fly about 

 as before. 



13. Put a cork into a square phial, and fix it 

 in with wax or cement ; put the phial on the pump 

 plate with the wire cage, and cover it with a close 

 receiver ; then exhaust the air out of the receiver, 

 and the air that was corked up in the phial will 

 break it outwards by the force of its spring, be- 

 cause there is no air left on the outside of the 

 phial to act against that within it. 



