PNEUMATICS. 143 



14. Put a shrivelled apple under a close receiver, 

 and exhaust the air ; then the spring of the air 

 within the apple will plump it out so as to cause all 

 the wrinkles to disappear ; but upon letting the 

 air into the receiver again, to press upon the apple, 

 it will return to its former decayed and shrivelled 

 state. 



1.5. Take a fresh egg y and cut off a little of the 

 shell and film from its smallest end ; then put the 

 egg under a receiver, and pump out the air; all 

 the contents of the egg will be forced out into the 

 receiver, by the expansion of a small bubble of air 

 contained in the great end, between the shell and 

 film. 



16. Put some warm beer into a glass, and hav- 

 ing set it on the pump, cover it with a close re- 

 ceiver, and then exhaust the air. Whilst this is 

 doing, and thereby the pressure more and more 

 taken off from the beer in the glass, the air therein 

 will expand itself, and rise up in innumerable 

 bubbles to the surface of the beer ; and thence it 

 will be taken away with the other air in the re- 

 ceiver. When the receiver is nearly exhausted, 

 the air in the beer, which could not disentangle 

 itself quick enough to get oft* with the rest, will 

 now expand itself so as to cause the beer to have 

 all the appearance of boiling ; and the greatest 

 part of it will go over the glass. 



17. Put some water into a glass, and a bit of 

 dry wainscot or other wood into the water ; then 

 cover the glass with a close receiver, and exhaust 

 the air ; the air in the wood having liberty to ex- 

 pand itself, will come out plentifully, and make all 

 the water to bubble, especially about the ends of 

 the wood, because the pores lie lengthwise. A 

 cubic inch of dry wainscot has so much air in it, 



