136 PARTIAL WATER TRESPASSERS. 



into it, the air that already exists is blown out, carry- 

 ing the cork with it. The only way to get the cork 

 into the bottlo is to coax it, so to speak, by blowing 

 very gently and steadily on one side, so that the air 

 within the bottle is allowed to escape gradually, and 

 the cork slowly rolls along the side of the neck until 

 it is fairly within the body of the bottle. 



These two examples illustrate the action of fur 

 upon the life of the animal, and show that the very 

 same property which keeps an animal warm in winter, 

 keeps it dry in water. In itself, fur has no warmth ; 

 and, if in the depth of winter, a thermometer were 

 applied to a fur coat and a steel cuirass, each would be 

 found to be of the same temperature ; though the 

 former would keep a man warm, and the latter freeze 

 him to death. Air is a very bad conductor of heat ; 

 and, as there is much air entangled in fur, it pre- 

 vents the animal heat from escaping. 



Thus we see why it is that long-haired furs are so 

 much warmer than those of a shorter character. 

 They entangle more air, and consequently interpose 

 more of a non-conducting medium between the animal 

 and the external cold. Even in these cases, such as 

 the seal-skin, in which ladies so rejoice, where the fur 

 is apparently short, the individual hairs are really 

 found to be long, but curled and twisted so as to 

 occupy less space, while holding the same amount of 

 air. A familiar example of the value of air as a non- 

 conductor of heat, may be seen in the conduct of birds 

 when exposed to severe cold. 



Take, for example, the redbreast a bird peculiarly 

 sensitive to cold, and so bold as to be easily ap- 



