SCIENCE OF COMMON THINGS. 151 



Cellars, why warm in winter and cool in summer. 



2. Because paint (especially white paint), being a 

 bad conductor, preserves tlie wood of a more uniform 

 temperature ; and 



3. Because it fills up the pores of the wood, and pre- 

 vents insects and vermin from harboring therein and 

 eating up the fibre. 



97*5 Why are furnaces and stoves (inhere much heat is required) built 

 of porous bricks f 



Because bricks are bad conductors, and prevent the 

 escape of heat / in consequence of which they are em?- 

 ployed where great heat is required. 



0*76 Why do cellars feel warm in winter 1 



Because the external air has not free access into them 1 5 

 in consequence of which they remain almost at an even 

 temperature, which (in winter-time) is about 10 degrees 

 warmer than the external air. 



97*7* Why do cellars fed cold in summer f 



Because the external air has not free access into them ; 

 in consequence of which they remain almost at an even 

 temperature, which (in summer-time) is about 10 de- 

 grees colder than the external air. 



97*8 Why do the Laplanders wear skins with the fur imvardsf 



Because the dry skin prevents the wind from pene- 

 trating to their body ; and the air (between the hairs 

 of the fur) soon becomes heated by the body / in conse- 

 quence of which the Laplander in his fur is clad in a 

 case of hot air, impervious to the cold and wind. 



97*9 In what respect is bark especially adapted as a covering for trees 

 and shrubs ? 



Bark is composed of matter which is. very slowly per- 

 meable by heat, and, like hair and fur in animals, is es- 

 pecially adapted for securing the temperature necessary 

 tg vegetable life. 



9SO What is the temperature of the sap of healthy trees during the 

 summer f 



It is several degrees below that of the surrounding at- 

 mosphere. 



981 What is the temperature of the sap of a healthy tree in tfie winter f 



