THE BEASON WHY. 



189 



1 A wise son heareth his father's instruction." PEOVEEBS xin. 



Because the lieat of the flame, 

 and the burning of the spirit, A, 

 create a volume of rare/ied, or thin 

 air, which inflates the balloon, and 

 makes it specifically lighter than 

 the surrounding medium. 



832. Why do balloons some- 

 times burst when they ascend 

 very high ? 



Because, as they get into the 

 thinner air, which exists at high 

 altitudes, the gas within them ex- 

 pands, and the coating of the balloon 

 is burcit asunder. 



Fig. 30. AIB-BAJLLOOX. 



833. Why does the gas of 

 balloons expand in thin air ? 



Because the air exerts a less amount of pressure upon the air or 

 gas contained in the balloons. 



834. Why do parachutes fall very gradually to the 

 ground ? 



Because the air, coming n con- 

 tact with, the under surface of the 

 expanded head of the parachute 

 resists its downward progress. 



835. Why does a shuttlecock 

 travel slowly through the air? 



Because the air acts upon the 

 feathers of the shuttlecock, in the 

 same manner as it does upon the 

 parachute it strikes against their 

 expanded surface, and resists their 

 progress through the air. 



836. Why does the shuttle- 



Fig. 31. PAPES PAKACHUTE. 



cock spin in the air ? 



