106 EFFECTS OF HEAT. 



Q. Where is all this quantity of AIR stowed 

 in the APPLE ? 



A. The inside of an apple is made up 

 of little cells (like a honey-comb}, each 

 of which contains a portion of the air. 



Q. When an APPLE is BOASTED, why is one 

 part made SOFT, while all the rest remains hard ? 



A. When an apple is roasted, the air 

 in the cells next to the fire is expanded 

 and flies out ; the cells are broken, and 

 their juices mixed together ; so the apple 

 collapses (from loss of air and juice), and 

 feels soft in those parts. 



Q. What is meant by the " apple COLLAPSING ?" 

 A. The plumpness gives way, and the 

 apple becomes flabby and shrivelled. 



Q,. Why do SPARKS of fire start (with a crack- 

 ling noise ) from pieces of WOOD laid upon a FIRE ? 



A. The air in the wood (expanded 

 by the heat), forces its way through the 

 pores of the log ; and carries along with 

 it the covering of the pore, which resisted 

 its passage. 



Q . What is meant by the ' ' PORES of the WOOD ?'' 



A. Very small holes in the 

 through which the sap circulates. 



