THE REASON WHY. 51 



" He casteth forth his ice like morsels : who can stand before his word." 

 PSALM CXLVIT. 



149. Why are woollen fabrics lad conductors of heat ? 

 Because there is a considerable amount of air occupying the 



spaces of the texture. 



150. Is air a good or a lad conductor ? 



Air is a bad conductor, and it chiefly transmits heat, as water 

 does, by convection. 



151. Is water a good or a lad conductor ? 



Water is an indifferent conductor, but it is a letter conductor 

 than air. 



152. Why, wlien we place our hands in water, which, may 

 le of the same temperature as the air, does the water fed 

 some degrees colder ? 



Because water, leing a letter conductor than air, takes up the 

 warmth of the hand more rapidly. 



153. Why, when we take our hands out of water do they 

 feel warmer ? 



Because the air does not abstract the heat of the hand so rapidly 

 as the water did, and the change in the degree of rapidity with 

 which the heat is abstracted produces a sensation of increased 

 loarmth. 



154. Why do we see blocks of ice wrapped in thick flannel 

 in summer time ? 



Because the flannel, being a non-conductor, prevents the external 

 heat from dissolving the ice. 



[Flannel wrapped around a warm body keeps in Us heat; and wrapped 

 around a cold body, prevents heat from passing into it."] 



155. Sow do we know that air is not a good conductor 

 of heat? 



Because, in still air, heat would travel to a given point much 

 more rapidly, and in greater intensity, through even an indifferent 

 solid conductor, than it would through the air. 



156. How do we know that water is not a good conductor 

 of heat? 



