WATER SHREW. 135 



would be perfectly justified. Taken alone, no amount 

 of hairs would keep water from the skin any more 

 than water could be carried in a sieve. But another 

 element has to be considered namely, the air which 

 entangled among the hairs, and which is the real 

 barrier both to the penetration of water to the skin, 

 and of loss of animal heat through the skin into the 

 water. 



Some of my readers may perhaps have tried to pour 

 water into an empty vessel through a single narrow 

 aperture, and, if they have done so, have signally failed, 

 the air in the vessel not permitting the water to enter. 

 Suppose, for example, that the vent-peg of an empty 

 barrel be removed, and a funnel tightly inserted in its 

 place. The funnel may be filled with water, but not a 

 drop will enter the barrel, the invisible air within 

 forming a barrier as effectual as a cork or a stopper. 



There is an amusing little trick which is sometimes 

 played upon unsuspecting persons, and which illus- 

 trates this property of air. An empty soda-water bottle 

 is laid on its side, and a piece of cork about as large 

 as a pea placed within the neck. Anyone is then 

 challenged to blow the cork into the bottle. This 

 looks so easy that a person who does not know the 

 trick, or whose knowledge of the properties of matter 

 does not enable him to see through the attempted 

 delusion, advances and blows sharply into the bottle. To 

 his great surprise he finds himself struck in the face 

 with the piece of cork, which he has blown out of the 

 bottle and not into it. 



The fact is, the bottle, although it looks empty, is 

 really full of air; and just in proportion as air is blown 



