SYSTEM OF MARINE CURRENTS. 25 



cold, How many thousands or even millions of cubic miles of 

 water may not the ocean contain, but these enormous masses, 

 too vast for the human imagination to conceive, are moved gently 

 but irresistibly by the power of a sphere 80,000,000 miles dis- 

 tant from our globe ! 



The influence of the oceanic currents upon the organic life, 

 not only of the seas but of the neighbouring lands, is quite incal- 

 culable. They moderate the heat of the tropical zone, and convey 

 a considerable portion of equatorial warmth into the higher 

 latitudes. Without the gulf-stream, whose influence may be 

 traced as far as the west coasts of Spitzbergen and Novaja 

 Sewlja, Scotland and Norway, where forests clothe the moun- 

 tain-sides up to a height of several thousand feet, would be 

 nothing but icy deserts ; and on the other hand, the tropical west 

 coast of South America owes its temperate climate to the cold 

 Peruvian stream, which constantly conveys refreshing coolness 

 from the Antarctic seas. 



It may easily be conceived how this vast system of currents 

 and counter-currents, furrowing the seas in every direction, must 

 contribute to the dissemination of marine life. Countless spores 

 of algae, innumerable eggs and larvas, are transported by the 

 oceanic, streams from place to place, and many land-animals 

 attached to floating timber are in a like manner conveyed to 

 distant regions. 



The ocean-currents are likewise extremely favourable to ma- 

 rine life, from their saturating the deep waters with atmosphe- 

 ric air ; for, as the colder superficial layers sink to the bottom, 

 they carry along with them the oxygen they have imbibed while 

 in contact with the air, and are thus able to impart this first 

 necessary of life to numerous animals dwelling in the deeper 

 waters. 



As the winds purify the atmosphere, thus also the currents 

 purify the sea by- preventing the accumulation of putrefying 

 substances and spreading them over a greater surface, where they 

 are speedily devoured by hosts of hungry scavengers. 



Besides all these beneficial influences, the marine currents 

 tend also to equalise the saline composition of sea- water, so 

 necessary to the welfare or existence of many of the denizens of 

 the ocean. 



Their movements also contribute to the formation of sand- 



