Bfr {Temperature. 53 



varying atmospheric conditions, is not a reli- 

 able mode of measurement. It is easily under- 

 stood that a cubic foot of air at sea-level will 

 contain a great many more atoms than a cubic 

 foot of air will at the top of a high mountain ; 

 or, to state it in another way, a cubic foot of 

 air at sea-level will occupy much more than a 

 cubic foot of space 10,000 feet higher up. 

 Suppose, then, that the amount of heat held 

 in a cubic foot of air at sea-level remained the 

 same, as related to the number of atoms. In 

 its ascent we shall find that at a high altitude 

 the same number of atoms that were held at 

 sea-level in a cubic foot have been distributed 

 over a so much larger space that the sensible 

 heat is greatly diminished or diluted, so to 

 speak. It was an old notion that heat would 

 hide itself away in fluids under a name called 

 by scientists latent heat. This theory has 

 been exploded, however, by modern investiga- 

 tion. 



If we place some substance that will inflame 

 at a low temperature in the bottom of what is 

 called a fire syringe (which is nothing but a 

 cylinder bored out smoothly, with a piston 

 head nicely fitted to it, so that it will be air- 

 tight) and then suddenly condense the air in 

 the syringe by shoving the plunger to the bot- 

 tom, we can inflame the substance which has 

 been placed in the bottom of the cylinder. In 

 this operation the heat that was distributed 



