[Sidenote:  Temperature as modified by oceans and winds.]

The zonal location of a country indicates roughly the degree of heat which it receives from the sun.  It would do this accurately if variations of relief, prevailing winds and proximity of the oceans did not enter as disturbing factors.  Since water heats and cools more slowly than the land, the ocean is a great reservoir of warmth in winter and of cold in summer, and exercises therefore an equalizing effect upon the temperature of the adjacent continents, far as these effects can be carried by the wind.  The ocean is also the great source of moisture, and this, too, it distributes over the land through the agency of the wind.  Where warm ocean currents, like the Gulf Stream and Kuro Siwa, penetrate into temperate or sub-polar latitudes, or where cool ones, like the Peruvian and Benguela Currents wash the coasts of tropical regions, they enhance the power of the ocean and wind to mitigate the extremes of temperature on land.  The warm currents, moreover, loading the air above them with vapor, provide a store of rain to the nearest wind-swept land.  Hence both the rainfall and temperature of a given country depend largely upon its neighboring water and air currents, and its accessibility to the rain-bearing winds.  If it occupies a marked central position in temperate latitudes, like eastern Russia or the Great Plains of our semi-arid West, it receives limited moisture and suffers the extreme temperatures of a typical continental climate.  The same result follows if it holds a distinctly peripheral location, and yet lies in the rain-shadow of a mountain barrier, like western Peru, Patagonia and Sweden north of the sixtieth parallel. [See map page 484.]

[Sidenote:  Effect of the westerlies.]

Owing to the prevalence of westerly winds in the Temperate Zones and particularly in the North Temperate Zone, the mean annual temperature is high on the western face of the northern continents, but drops rapidly toward the east.[1417] This is especially true of winter temperatures, which even near the eastern coast show the severity of a continental climate.  Sitka and New York, Trondhjem and Peking have the same mean January temperatures, though Peking lies in about the latitude of Madrid, over twenty-three degrees farther south.

Europe’s location in the path of the North Atlantic westerlies, swept by winds from a small and narrow ocean which has been super-heated by the powerful Gulf Stream, secures for that continent a more equable climate and milder winters than corresponding latitudes on the western coasts of North America, whose winds from the wide Pacific are not so warm.[1418] Moreover, a coastal rampart of mountains from Alaska to Mexico restricts the beneficial influences of the Pacific climate to a narrow seaboard, excludes them from the vast interior, which by reason of cold or aridity or both must forever renounce great economic or historical