XII. 



THE GREAT UNKNOWN. 



A SAILOR lad, after his first voyage, having returned to 

 his country home, was eagerly beset for wonders. "What 

 hast t' seen in f urrin parts ? " Among other things he 

 reported having been where the rum flowed like rivers, and 

 sugar formed whole mountains. At last, his inventive 

 powers being exhausted, he began to speak of the shoals 

 of tropical flying-fishes, a phenomenon which his familiar 

 sight had long ceased to regard as a wonder. But here 

 his aged mother thought reproof needful ; raising her 

 horn spectacles, and frowning in virtuous indignation, she 

 said, " Nae, nae, Jock ! mountains o' sugar may be, and 

 rivers o' rum may be ; but fish to flee ne'er can be ! " 



Old Dame Partlet did only what philosophers in all ages 

 have done ; she had formed her schedule of physical 

 possibilities, outside of which nature could not go ; nay, 

 must not go. It so happened, however, that old Dame 

 Nature was obstreperous, and refused to be confined within 

 possibilities ; and the lawless fishes fly to this day, in spite 

 of Dame Partlet's virtuous protest. 



There are several questions in natural science which are 

 questiones vexatce, because a certain amount of evidence 

 of facts is on one side, and a certain amount of presuinp- 



