MIND UNDER WATEB. 163 



themselves to altered circumstances which they could 

 not foresee, and the knowledge how to meet which 

 could not have been inherited. The basking jack is 

 not alarmed at the cart-horse's hoofs, but remains 

 quiet, let them come down with ever so heavy a thud. 

 He has observed that these vibrations never cause 

 him any injury. He hears them at all periods of the 

 day and night, often with long intervals of silence and 

 with every possible variation. Never once has the 

 sound been followed by injury or by anything to dis- 

 turb his peace. So the rooks have observed that 

 passing trains are harmless, and will perch on the 

 telegraph wires or poles over the steam of the roaring 

 locomotive. Observation has given them confidence. 

 Thunder of wheels and immense weight in motion, 

 the open furnace and glaring light, the faces at the 

 long tier of windows — all these terrors do not ruffle a 

 feather. A little boy with a wooden clapper can set 

 a flock in retreat immediately. Now the rooks could 

 not have acquired this confidence in the course of 

 innumerable generations; it is not hereditary; it is 

 purely what we understand by intelligence. Why 

 are the rooks afraid of the little boy with the clapper ? 

 Because they have noticed his hostile intent. Why is 

 the basking jack ofi* the instant he hears the light 

 step of a man ? 



He has observed that after this step there have 

 often followed attempts to injure him; a stone has 

 been flung at him, a long pole thrust into the water ; 

 he has been shot at, or felt the pinch of a wire. He 

 remembers this, and does not wait for the attempt 

 to be repeated, but puts himself into safety. If he 



