220 FERGUSON'S LECTURES. 



LECT. neck downward into the empty phial a a, and covered it 



.^v-'x^ with a close receiver, exhaust the air out of the receiver, 



and the small bubble of air in the top of the ball will 



expand itself, so as to force all the water out of the ball 



into the phial. 



17. Screw the pipe A B into the pump-plate, place 

 the tall receiver GH upon the plate c d, as in the 

 twelfth experiment, and exhaust the air out of the re- 

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

 screw the pipe from the pump, and screw it into the 

 mouth of the copper vessel C C, the 



vessel having first been about half filled 

 with water. Then open the cock e 

 (page 218) 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 in a bason, in 

 the twelfth 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 with a great weight, then 

 grow convulsed, and at last expire in all the agonies of 

 a most bitter and cruel death. But as this experiment 

 is too shocking to any spectator who has the least 

 degree of humanity, we substitute a machine called the 

 lungs-glass in place of the animal. 



19. 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 the receiver continues full of 

 air ; 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 mid- 

 dle of the receiver, until the air be let in again, and 

 then the animal will fly about as before. 



