210 THE WONDEEFUL HOUSE THAT JACK HAS 



conductors of heat, and hence make cooler clothing. 

 Because of the non-conducting power of dry air, two 

 or more thin garments or quilts are warmer than one 

 of thickness equal to all the others. For a similar 

 reason, a loose garment is warmer than a tight-fitting 

 one. 



Woolen naturally contains numerous air spaces, and 

 so is warm clothing. Cotton, linen, and silk, being 

 usually more closely woven, are cooler clothing. When 

 any of the last three is woven into a mesh-like cloth 

 containing numerous air spaces, it is much warmer 

 clothing than in the ordinary close weave. Dark- 

 colored cloth absorbs the sun's rays to a much greater 

 extent than fabric of light color, and, for that reason, 

 is warmer. These facts explain why fur and woolen 

 material are so generally worn in cold weather, and 

 light-colored cotton and linen in the warm months. 



In a previous chapter, we read how the numerous 

 pores of the skin are continually giving out perspira- 

 tion containing bodily waste and impurities. On this 

 account, most civilized people wear next to the skin 

 underclothing of such weight and texture that it 

 can be easily and frequently washed. Undergarments 

 should not allow heat to pass off too quickly from our 

 bodies. Neither should they prevent its passing 

 to such a degree that any portion of the body will 

 become uncomfortably warm. Underwear should also 

 take up moisture readily and permit its rapid evapo- 

 ration. This is important, because, as moist air is a 



