198 SCIENCE OF COMMON THINGS. 



Health injured by reducing the temperature of the body. 



surface of our body to convert the damp of the sheets 

 into vapor ; in consequence of which our animal heat 

 is reduced 'below the healthy standard. 



1309 Why is health injured when the temperature of the body is 

 reduced below its natural standard f 



Because the balance of the circulation is destroyed. 

 Blood is driven away from the external surface by the 

 chill, and thrown upon the internal organs, which are 

 oppressed by this increase of Hood. 



1310 Why do we not feel the same sensation of cold if we throw a 

 waterproof coat over our wet clothes f 



Because water-proof coats (being air-tight) prevent 

 evaporation, and (as the wet cannot evaporate) no heat 

 is absorbed from our bodies. 



1311 Why does sprinkling a hot room with water cool it f 



Because the heat of the room causes a rapid evapora- 

 tion of the sprinkled water, and as the water evaporates, 

 it absorbs heat from the room, which cools it. 



131J3 Why does watering the streets and roads cool them f 



Because they part with their heat to promote the eva- 

 poration of the water spi^inkled on them. 



1313 Why does a shower of rain cool the air in summer-time ? 



Because the wet earth parts with its heat to promote 

 evaporation y and when the earth is cooled, it cools the 

 air also. 



1314 Why is linen dried by being exposed to the wind f 



Because the wind accelerates evaporation by removing 

 the vapor from the surface of the wet linen as fast as it 

 is formed. 



1315 Why does draining land promote warmth, 



Because abstracting water diminishes evaporation ; 

 in consequence of which less heat is withdrawn from the 

 earth. 



1310 Why does cultivation increase'the warmth of a country f 



A cultivated country is better drained, and laid open 

 to the rays of the sun. The forests being cut down, 

 the snow quickly disappears in the spring, and the 

 earth soon becomes dry. 



