THE BEASON WHY. 



" Though. I walk in the valley of the shadow of death I will fear no evil, for thou 

 art with me." PSALM xxur. 



and being followed by another portion of air, a further amount of 

 heat is borne away. 



176. Is the atmosphere ever as hot as the human body ? 



Not in this country. On the hottest day it is 10 or 12 deg. 

 cooler than the temperature of our bodies. 



177. What is the highest degree of artificial heat which 

 man has been known to bear ? 



A man may be surrounded with air raised to the temperature of 

 300 deg. (the boiling point being 212), and yet not have the heat 

 of his body raised more than two or three degrees above its natural 

 temperature of from 97 deg. to 100 deg. 



178. Why may man endure this degree of heat for a short 

 time ivithout injury ? 



Because the skin, and the vessels of fat that lie underneath it, 

 are bad conductors of heat. 



And because perspiration passing from the skin and evaporating, 

 would bear the heat away as fast as it was received. 



Because, also, the vital principle (life) exercises a mysterious influ- 

 ence in the preservation of living bodies from physical influences. 



179. Is the air ever hot enough, in any part of the world, 

 to destroy life ? 



Yes. The hot winds of the Arabian deserts, which are called 

 simooms, scatter death and desolation in their track, withering trees 

 and shrubs, and burying them under waves of hot sand. When 

 camels see the approach of a simoom they rush to the nearest tree 

 or bush, or to some projecting rock, where they place their heads in 

 an opposite direction to that from which the wind blows, and en- 

 deavour to escape its terrible violence. The traveller throws him- 

 self on the ground on the lee side of the camel, and screens 

 his head from the fiery blast within the folds of his robe. But fre- 

 quently both man and beast fall a prey to the terrible simoom. 



180. Why are these hot winds so terrible in their effects ? 

 Because, being in motion, they ssarch their way to every part of 



