58 CHEMICAL ACTION. 



heat, as water is squeezed from a sponge ; 

 and as the goods of a large pile are 

 greatly compresssd, much of their latent 

 heat is squeezed out. 



Q. Why do HAY-STACKS sometimes CATCH FIEE 

 of themselves ? 



A. Either because the hay was got 

 up damp, or because rain has penetrated 

 the stack. 



Q. Why ivill a HAY-STACK CATCH FIKE if the 

 hay be damp ? 



A. Damp hay soon decays, and 

 undergoes a state of fermentation ; during 

 which, carbonic acid gas is given off, and 

 the stack catches fire. 



Q. Why does roasted COFFEE sometimes CATCH 

 FIRE spontaneously ? 



A. The heat of coffee is greatly 

 increased by being roasted; and the 

 carbon of the coffee uniting with the 

 oxygen of the air, produces carbonic 

 acid gas, and bursts into flame. 



Q. Why do old RAGS, used for CLEANING 

 LAMPS and CANDLES, sometimes set a HOUSE on 



FIRE? 



