130 EFFECTS OF HEAT. 



even the earth : but the average height 

 is between one and two miles. 



(Streaky curling clouds, like hair, are often five or 

 six miles high.) 



Q. WHAT CLOUDS are the LOWEST ? 



A. Those that are most highly elec- 

 trified : lightning clouds are rarely more 

 than about 700 yards above the ground ; 

 and very often actually touch the earth 

 with one of their edges. 



Q. What is the THICKNESS of the CLOUDS ? 



A. Some clouds are 20 square miles 

 in surface, and above a mile in thickness ; 

 while others are only a, few yards or inches. 



Q. How can persons ascertain the thickness of 

 a cloud ? 



A. As the tops of high mountains are 

 generally above the clouds; therefore, 

 travellers (who climb the mountains) may 

 pass quite through the clouds, into a clear 

 blue firmament, when they may see the 

 clouds beneath their feet. 



Q. Why are the CLOUDS so VARIABLE in 

 SHAPE ? 



A. The shape of clouds depends upon 

 two things: Their state of electricity, 

 and the wind. 



