THE EUROPEAN SEAS. 



57 



which now prevail on our side of the ocean. But 

 there has also been a march in the opposite direc- 

 tion, for we find some few littoral shell-fish (Trochus 

 cinerarius, Rissoa interrupta, Patella pellucida, and 

 the common cockle, Cardium edule), extending from 

 the coasts of France to Finmark, but not reaching 

 Greenland ; whilst, as we shall see in our account 

 of the Boreal province, others do not get so far. 

 The common limpet (Patella vulgata) is said not to 

 extend beyond Nordland, and the larger periwinkle 

 (Littorina littorea), advances as far as Yadsoe. 



These are small facts, but they have a large 

 significance. The student of history follows, with 

 intense interest, the march of a conqueror, or the 

 migrations of a nation. The traveller traces with 

 almost breathless delight, every step of the progress 

 of some mighty hero of ancient days. I have had 

 my share of the pleasure when tracking the course 

 of Alexander and his armies in Pisidia, and deter- 

 mining mile by mile the route of Manlius through 

 Milias ; on ground, too, to the modern geographer, 

 wholly new. Yet, absurd as it may seem to those 

 who have not thought of such things before, there is 

 a deeper interest in the march of a periwinkle, and 

 the progress of a limpet. It is easier to understand 

 how the son of Philip made his way safely through 

 the sea, on his famous march from Phaselis, than 

 to comprehend how the larva of a Patella crossed 

 the fathomless gulf between Finmark and Green- 

 land. It is a strong saying, but not said without 



