130 SEVENTEENTH CENTURY. FT. m. 



atmosphere, but existed in nitre, or saltpetre, and also in 

 many acids ; and then he set to work to discover how much 

 of it there was in ordinary air. To do this he took a piece 

 of camphor, with some tinder dipped in melted sulphur, 

 and placed it on a little platform hung inside a bell-jar (sec 

 Fig. 20). He then lowered the bell-jar into a basin of 

 water, having first put a siphon or bell-tube under the bell- 

 jar to let out enough air for the water to rise. Then he 

 took the tube out, leaving the water at the same height 

 inside and outside the jar, while the rest of the jar above 



FIG. 20. FIG. 21. 



Mayow's experiments on combustion and respiration (Yeats). 



the water was full of air. He now held up a burning-glass, 

 and brought the sun's rays to a focus upon the camphor and 

 tinder till it grew hot and burst into a flame. As it burnt 

 he noticed that at first the water inside the jar sank down, 

 because the air, being heated, expanded and took up more 

 room. Then after a time the camphor ceased to burn, the 

 jar cooled down, and the water rose again higher than before, 

 till it stood above the water outside. The camphor was not 

 all consumed, but when he tried to light it again he could 

 not succeed. Why was this ? ' Because,' said Mayow, 

 * there are r\u fire-air particles left in the jar to make the 



