NATURE IN MOTION. 67 



well adapted to swift and easy motion, that the unavoid- 

 able resistance of the fluid in which they travel, never 

 seems to impede their progress. While birds, when they 

 undertake long flights, are often obliged to alight, and 

 even try to rest on the yards of vessels, fishes never 

 seem to be exhausted by fatigue and to require respite 

 or repose. Sharks are known to have kept pace with 

 fast-sailing ships during whole long voyages, and to have 

 sported around them as in mockery. 



For known and for unknown purposes, in the tiny moun- 

 tain brook, and in the wide ocean, fishes are seen in un- 

 ceasing motion, darting in all directions, travelling now 

 single, and now in shoals. Their regular journeys are 

 mostly undertaken for the purpose of spawning; the deli- 

 cate mackerel moves southward when its time comes, and 

 the beautiful sardine of the Mediterranean goes, in spring, 

 westward, and returns in autumn to the east. The stur- 

 geon of northern Europe is seen singly to ascend the 

 great rivers of the Continent, and the ormul, or migra- 

 tory salmon of the polar seas, travels, we know not how, 

 through river and lake, up into the Baikal, and there 

 swims, in whimsical alternations, but always in immense 

 crowds, first on the southern and then on the northern 

 bank. The travels of the salmon are probably best known, 

 because the fish was a favorite already in the days of 

 Pliny, and yet, strange enough, is found in every sea in 

 the Arctic, near the equator, and off New Holland, only 

 not in the Mediterranean. They press in large, triangular 

 masses up all the great northern rivers of Europe, Asia, 

 and America. They enter Bohemia with Shakespeare, by 



