Page:Popular Science Monthly Volume 76.djvu/254

250 be made here of a peculiar relation between climate and man in the case of certain tropical mountains which are high enough to receive snow instead of rain on their upper slopes. These mountains furnish a supply of snow and ice for refrigerating purposes in the towns below them. Thus, in Ecuador, snow is carried to Quito from the upper slopes of Pichincha; to Riobamba and Ambato from the slopes of Chimborazo. Guayaquil was formerly supplied with ice in the same way. In Colombia, Popayan, in the department of Cauca, is also supplied with ice and snow from the neighboring mountains. In Mexico, snow is carried from the summit of Colima to the towns on the hot plains below. The occupation of the Indians who bring down this ice from their tropical mountain tops is a curious example of climatic control.

Characteristics of the Temperate Zones.—The so-called "temperate zones" occupy about one half of the earth's surface. The north temperate zone includes the greatest known extremes of temperature, and if the word "temperate" were not so firmly established it would be well to change the name to "intermediate." A marked changeableness of the weather is a striking characteristic of these zones. For most of the year, and most of the temperate zones, settled weather is unknown. Climate and weather are here by no means synonymous. The changeableness of the weather suggests our never-failing subject of conversation. In the tropics no one talks about the weather, for it is monotonously the same, day after day.

In the north temperate zone the differences in temperature between the warmest and coldest months reach 120° at their maximum, in northeastern Siberia. An average January temperature of—60° and an average July temperature of 95°, with maxima of over 120° and minima lower than—90°, occur in this same zone.

The prevailing winds of the "temperate zones" are the westerlies, which occupy about as much of the earth's surface as do the easterly trades. The westerlies are, however, less regular than the trades, being much confused and interrupted by storms. So common are such interruptions that the prevailing westerly wind direction is often difficult to discern without careful observation. The south temperate zone is chiefly water. Hence the westerly winds are there but little interfered with by land. "Roaring forties" is a well-known designation for the southern middle latitudes, and between latitudes 40° and 60° south the well-named "brave west winds" blow with a constancy and a velocity hardly known in the northern hemisphere. Storms, frequent and severe, characterize these southern hemisphere westerlies. Voyages to the west around Cape Horn against head gales, and in cold, wet weather, are much dreaded, and are apt to be long and dangerous.

Between the trades of the tropics and the westerlies of the