222 FERGUSON'S LECTITRES. 



LECT. L Then, turn the cock d to shut out the air, unscrew 

 x-v-x^ the machine from the pump, and having screwed it to 

 the wooden foot L, put the receiver K upon the plate 

 h; this receiver will continue loose on the plate as long 

 as it keeps full of air ; which it will do until the cock 

 i? be turned to open the communication between the 

 pipes jPand E, through the trunk A B ; and then the 

 air in the receiver K, having nothing to act against its 

 spring, will run from K into /, until it be so divided 

 between these receivers, as to be of equal density in 

 both ; and then they will be held down with equal 

 forces to their plates by the pressure of the atmo- 

 sphere ; though each receiver will then be kept down but 

 with one half of the pressure upon it, that the receiver / 

 had, when it was exhausted of air ; because it has now 

 one half of the common air in it which filled the re- 

 ceiver K when it was set upon the plate ; and therefore, 

 a force equal to half the force of the spring of common 

 air^ will act within the receivers against the whole 

 pressure of the common air upon their outsides. This 

 is called transferring the air out of one vessel into 

 another. 



22. Put a cork into the square phial A (page 219,) 

 and fix it in with wax or cement ; put the phial upon 

 the pump-plate with the wire cage B over it, and cover 

 the cage with a close receiver. Then, exhaust the 

 air out of the receiver, and the air that was corked 

 up in the phial will break the phial outwards by the 

 force of its spring, because there is no air left on the 

 outside of the phial to act against the air within it. 



22. 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 instantly return 

 to its former decayed and shrivelled state. 



23. Take a fresh egg, and cut off a little of the shell 



