CH. xvi. RESPIRATION AND COMBUSTION. 131 



camphor burn, and the using up of these particles has made 

 the rest of the air shrink and take up less space.' 



He now wished to compare burning with breathing, so 

 he put a mouse in a cage and hung it inside the bell-jar, 

 which he arranged over the water as before. Little by little 

 as the mouse breathed the water crept up inside the jar, 

 until when it had risen to a certain height the mouse drooped 

 and died. It was clear, therefore, that animals in breath- 

 ing use up some portion of the air. But is it the same 

 portion which the flame uses? Many people would have 

 jumped at this conclusion, but Mayow was not content till 

 he had proved it by another experiment. He put a lighted 

 candle and a mouse together inside the bell-jar. The water 

 now rose much faster than before ; the candle went out first, 

 and then the mouse drooped as soon as the water had risen 

 to the same height as in the other experiment. He was 

 now certain that the candle and mouse both used up the 

 same fire-air particles ; but to make still more sure, he put 

 a candle under a bell-jar where the air had been spoiled by 

 breathing, and it went out directly. 



His next step was to try whether air was lighter or 

 heavier after the fire-air had been used up. To do this he 

 put two mice into the jar, one at the top and the other at 

 the bottom ; the one at the top drooped and died, while the 

 other was still breathing. This proved that the air which 

 had lost \\sfire-air particles was lighter and rose to the top, 

 so that the top mouse could no longer breathe. By these 

 and a great many other experiments Mayow proved that air 

 is made up of two portions the one which supports flame and 

 life being comparatively heavy ; and the other light and use- 

 less for burning or breathing : this last was the largest portion. 

 I want you to notice this particularly, because you will see 

 by arid by that Mayow had really discovered and described 

 ii 



