110 EFFECTS OF HEAT. 



Q. Why does the BALLOON RISE, after it has 

 been inflated by the expanded air ? 



A. The same quantity of air is 

 expanded to three or four times its 

 original volume; and is made so much 

 lighter than common air, that even when 

 all the paper, wire, and cotton are added, 

 it is still lighter bulk for bulk. 



Q. What is meant by being lighter " bulk for 



bulk r 



A. If the balloon be 3 square feet in 

 size, it is tighter (when inflated) than 3 

 square feet of common air, and therefore 

 floats through it ; as a cork (at the bottom 

 of a tub of water) would rise to the 

 surface. 



Q. Why does SMOKE RUSH UP a CHIMNEY ? 



A. The heat of the fire expands the 

 air in the chimney; and (being thus 

 made lighter than the air around), it 

 rises up the chimney, and carries the 

 smoke in its current. 



Q. Why has a LONG CHIMNEY a greater 

 DRAUGHT than a short one ? 



A. Because air rises faster and faster 

 the higher it ascends in a chimney flue ; 



