464 POWER OF CALCULATION. 



angle, so as to produce a recoil of its blast which brings the 

 coin within reach of its trunk. 



By their combined efforts at mechanical labour, more- 

 over, ants act upon the principle of union or aggregate 

 strength (Watson). 



The use of counterpoise is seen occasionally in spiders, 

 for instance when they suspend from one angle of a web a 

 small fragment of stone, to keep it on the proper stretch. 

 Thus a correspondent of ' Nature ' describes one as having 

 suspended to its web a fragment of gravel as a movable 

 weight, to counteract the effect of gusts of wind. The rose- 

 leaf-cutter bee fixes pieces of rose-leaf to her cell, ' solely by 

 calculating upon the natural spring of the leaf, and so ad- 

 apts the pieces that the middle one always overlies a join in 

 the others ' (Milton). 



Dogs at least calculate and make allowance for the 

 rapidity and strength of currents of rivers and tides. Thus 

 Wood describes a miller's dog that, to save a drowning small 

 one, ran by the side of a certain river till it ' got well below 

 the drowning dog : ' then it sprang into the river and swam 

 across : ' and so exactly had he calculated the rapidity of the 

 river, and his own speed, that he intercepted the little dog 

 .... and brought it safely to land.' 



The old mare or cow forms very shrewd estimates of 

 weakness in, discovers the weak points of, a fence that debars 

 access to tempting fodder (Macaulay). The dog and other 

 animals form estimates both of their own strength in relation 

 to size of body, and that of their fellows, so as to judge, 

 for instance, how far they can cope with them as rivals or 

 enemies. Hence they acquire a consciousness of great supe- 

 riority of size and strength, which probably leads the large 

 powerful dog to decline fighting with a small weak one, a 

 phenomenon usually attributed to a display of magnanimity. 

 They become aware when they have met their c match ; ' 

 when honorable and equal combat may be the result. And 

 in other cases, they are convinced of the futility of effort, of 

 the inadequateness of their strength. 



The horse and other animals of burden compare their 

 own strength, or physical agility, with the size, weight or 



