148 SCIENCE OF COMMON THINGS. 



Why wool, hair, and feathers are warm. Icehouses. 



gradually draw away its heat, till it was as cold as the 

 air itself. 



953 What, then, is the principal use of clothing in winter-time? 



1. To prevent the animal heat from escaping too 

 freely ; and 



2. To protect the body from the external air (or wind), 

 which would carry away its heat too rapidly. 



954 Why are ivool, fur, hair, and feathers such slow conductors of heat f 



Because a great quantity of air lurks entangled 

 between the fibres ; and air is a very bad conductor of 

 heat. 



The warmest clothing is that which fits the body rather loosely, because 

 more hot air will be confined by a moderately loose garment than by one 

 which fits the body tightly. 



955 How are whales,seals, and other iv arm-blooded animals that live in 

 the water protected against the cold f 



They are enveloped, beneath the sJcin, with a thick 

 coating of " blubber" or fat, which, like fur, hair, and 

 feathers, is a non-conductor of heat, and serves to pro- 

 tect them in like manner. 



95G Why are blankets and warm woollen goods always made with a 

 nap cr projection of fibres on the outside ? 



Because the nap or fibres retain air among them, 

 which, from its non-conducting properties, serves to 

 increase the warmth of the material. 



How does the covering of hair, wool, and feathers serve to keep ani- 

 mals cool in hot weatlier, as well as warm in cool weather ? 



In warm w^eather the non-conducting medium will 

 not allow the heat to enter the \to&y from without : in 

 cold weather the heat of the body cannot escape from 

 within. 



958 Why do we wrap up ice in flannel to Jceep it from melting f 



Because the flannel, being a non-conductor, does not 

 allow the heat of the atmosphere to penetrate to the ice. 



959 In the construction of icehouses, why do we line the walls and roof 

 with straw or sawdust % 



Because these substances are bad conductors of heat, 



960 Why is it good economy to furnish our houses in winter with double 

 windows t 



