THE NON-LIVING WORLD 157 



The greater oceans contain abysses which sink much 

 deeper below the ocean's level than any mountains 

 ascend above it. With these complex conditions of shore 

 and sea-bottom, it is no wonder that ocean currents 

 become thereby variously diverted from the courses they 

 would take were they affected by nothing but varia- 

 tions of temperature. Nevertheless difference of tem- 

 perature is the great cause of their existence, while one 

 of their most noteworthy effects is the great change they 

 can produce in land climates. Thus while cold currents 

 sweeping down from the Greenland seas, carry ice and 

 cold water southwards along the east coast of America, 

 to 40 of north latitude, the equatorial current (proceed- 

 ing westwards across the Atlantic and northwards to 

 the Gulf of Mexico) and, its prolongation, the Gulf 

 Stream (extending north-eastwards from the Mexican 

 Gulf) carry warmth with their waters into western Europe 

 and over the North Cape. Did a belt of land extend 

 between Britain and Greenland, so as to intercept the 

 passage of this warm stream (as the land bounding 

 Behring Straits stays the passage northwards of the 

 warm currents of the Pacific Ocean), we should then see 

 the mountains of Scandinavia (like those in Greenland 

 in nearly the same degree of latitude) permanently 

 covered with ice and snow. 



The elevations of the land mountain chains exert 

 various effects on currents of air the winds analogous 

 to those produced by the form of coasts on ocean 

 currents. Mountains are sometimes very lofty, the 

 highest in the world, those of the Andes, rise close on 

 30,000 feet, while Himalayan peaks exceed 27,000. 

 The direction of mountain chains is also most influential. 

 No line of mountains running east and west in North 

 America, checks the descent of polar winds to the Gulf 



