EXPANSION BY HEAT. 105 



this spirit-lamp it will only go in the gauge or 

 through the hole with difficulty ; and if I were 

 to put it into boiling-water it would not go 

 through at all. Again ; as soon as the heat 

 escapes from bodies they collapse ; see how the 

 air is contracting in the vessel now that Mr. 

 Anderson has taken away his lamp : the stem 

 of it is filling with water. Notice too, now, that 

 although I cannot get the tube through this 

 hole or into the gauge, the moment I cool it by 

 dipping it into water, it goes through with per- 

 fect facility, so that we have a perfect proof of 

 this power of heat to contract and expand bodies. 



