52 THE REASON WHY. 



As snow in summer, and as rain in harvest ; so honour is not seemly for a 

 fool." Pitov. xxvi. 



Because in a deep vessel containing ice, and with heat applied at 

 the top, some portion of the water may be made to boil before the 

 ice, which lies a little under the surface, is melted. 



157. Why would you apply the heat at the top, in this 

 experiment ? 



Because in heating- water it expands and rises. The boiling of 

 water is caused by the heated water ascending from the bottom, 

 and the colder water descending to occupy its place. If the heat 

 were not applied at the top, it would be distributed quickly by 

 convection, but not by conduction. 



158. Why are bottles of hot water, used as feet-warmers, 

 ivrapped in flannel ? 



Because the flannel, being a bad conductor, allows the heat to 

 pass only gently from the bottle, and preserves the warmth for a 

 much longer time. 



159. Wliy are liot rolls sent out by the bakers, wrapped 

 up in flannel ? 



Because the flannel, being a bad conductor, does not carry off 

 rapidly the heat of the rolls. 



160. Why is it said that snow keeps the earth, warm ? 



Because snow is a bad conductor, and prevents the frosty air 

 from depriving the earth of its warmth 



161. Why are snow huts wliicli the Esquimaux build 

 found to be warm ? 



Because snow, being a bad conductor, keeps in the internal heat 

 of the dwelling, and prevents the cold outer air from talcing away 

 its warmth. 



162. Why is snow, leing composed of congealed water 

 (and water being a better conductor than air), so good a non- 

 conductor ? 



Because in the process of congealation it is frozen into crystaline 

 forms, which, being collected into a mass, form a woolly body, thus 



