462 POWER OF CALCULATION. 



well as of the size of their prey, being involved. They learn 

 by experience to make due allowance for the refraction of 

 light by water ; to use their natural weapon, the syringe, in 

 the operation of squirting ; and to employ water as an effec- 

 tive kind of shot, missile or projectile (Houzeau). But the 

 archer-fish, in the precision of its aim, makes allowance, not 

 only for the refraction of light and for distance: not only 

 for the size, but also for the movements of its victims 

 (Baird), while the dog and other animals make proper al- 

 lowance for wind and water currents. The elephant makes 

 a similar use of his trunk as a syringe or hydropult, and of 

 water as a projectile : while it also estimates distance and 

 size in the occasional punishment of his human tormentors. 

 Both in the archer-fish and the elephant, calculation of dis- 

 tance amounts to, or involves, an estimation of the range of 

 projectiles, as well as of the force necessary for the projec- 

 tion of missiles. 



Many animals learn by experience the average or maxi- 

 mum range of man's projectiles or explosives, of his firearms 

 and their contents, especially : and they have or acquire the 

 sense to keep for their own safety beyond range. They cal- 

 culate this range with great nicety in certain cases. Thus 

 the dog in a farrier's smithy will be found sometimes just far 

 enough from the forge or furnace to be beyond danger from 

 fire sparks, but yet sufficiently near to get the full benefit of 

 the grateful heat. The crow and other birds dread man 

 within rifle range, if he carries a rifle ; but are perfectly un- 

 concerned if they keep and feel themselves beyond bullet 

 reach. 



A calculation of range is implied in various devices of the 

 fox, or other animals, for bringing their prey within captur- 

 ing reach. There is correct judgment of distance in the 

 feints of a partridge ; as well as of time in relation to space 

 in the journeys of Texan cattle to their watering ground. 

 They time their setting out according to the distance they 

 have to travel (Houzeau). 



There is even a nicer calculation of time and space in the 

 robbery of the fish hawk by the eagle (' Percy Anecdotes'). 

 In the Arctic bear, which kills the walrus by rolling down 



