48 G THE LAWS OP ORIENTATION AMONU ANIMALS. 



there food and rest. When set at liberty he finds his way back to it 

 with the constancy of the magnetic needle turning to the pole. 



The horse knows perfectly the road back to his home. If in the 

 course of a drive the reins are let to fall loose on his neck he will take 

 this opportunity of returning to his stable. With the help of an excel- 

 lent memory he knows the comparative length of the roads to be fol- 

 lowed, and chooses without hesitation the shortest. 



Suppose that the same horse is taken into a country of which he is 

 ignorant. After a stay of some hours in a stable he develops the same 

 attachment for his new home which he showed for the former. If in 

 the first drive he is left to his instinct to find his way back it has been 

 ascertained that he will follow the same road, reversed, by which he 

 came, even if it is not the shortest. 



Third. The carrier pigeon when set loose within a short radius of its 

 home will return to its cote by the shortest way. If it is set at liberty 

 some hundreds of miles from its home it follows in its return very 

 exactly the line of the railroad by which it came. We need no further 

 proof of this than the following fact. 



In the season of the conventions of pigeon fanciers the inhabitants 

 of Bapaume remarked the flight every Sunday of numerous bands of 

 pigeons returning to their homes in the north of France, or in Belgium. 

 We can not claim that Bapaume is exactly on the straight line that 

 connects the different points from which the pigeons were let loose to 

 their dovecotes scattered throughout the region of the north, from 

 Dunkerque to Mezieres. It was not merely choice that thousands of 

 pigeons should pass every Sunday over the little city. Bapaume is 

 only an insignificant point in the very extended zone which separates 

 Belgium from the center of France. Moreover, from similar observa- 

 tions made at Amiens, at Arras, and all along the line of the route from 

 Paris to Brussels, it was proven that the pigeons retraced in a contrary 

 direction the road by which they had been taken to the place of 

 release. 



We might cite any number of observations of the same sort. For 

 example, the employees of the Orleans railway have often told us of the 

 passage to Arthenay, to Etampes, or to Juvisy of Belgian pigeons 

 released at Poitiers, Angouleme, and Bordeaux. 



We have deduced from these facts the following hypothesis, which 

 we will call the "law of retracement." The instinct of orientation from 

 a distance is a faculty which all animals possess in different degrees, of 

 retracing a route over which they have once passed. 



IV. 



In the study of mathematics the method is often employed of con- 

 sidering a proposition as demonstrated, then stating it in the form of a 

 problem and studying out the consequences. We will use this method 

 here. Lei us admit that the hypothetical law stated above has been 



