54 flaturc'0 



through the whole body of air, that was con- 

 tained in the cylinder before it was com- 

 pressed, is now condensed into a small space. 

 If we withdraw the plunger immediately, be- 

 fore the heat has been taken up by the walls of 

 the syringe, we shall find the air of the 

 same temperature as before the plunger was 

 thrust down. This, however, does not take 

 into account any heat that was generated by 

 friction. 



Let us further illustrate the phenomenon by 

 another experiment. If we suddenly compress 

 a cubic foot of air at ordinary pressure into a 

 cubic inch of space, that cubic inch will be 

 very hot because it contains all the heat that 

 was distributed through the entire cubic foot 

 before the compression took place. Now let 

 it remain compressed until the heat has radi- 

 ated from it, as it soon will, and the air be- 

 comes of the same temperature as the sur- 

 rounding air. What ought to happen if then 

 we should suddenly allow this cubic inch of 

 air to expand to its normal pressure, when it 

 will occupy a cubic foot of space? 



Inasmuch as we allowed the heat to escape 

 from it when in the condensed form, when it 

 expands it will be very cold, because the heat 

 of the cubic inch, now reduced to the normal 

 temperature of the surrounding air, is dis- 

 tributed over a cubic foot of space. 



This is precisely what takes place when 



