Page:All Over Oregon and Washington.djvu/279

Rh evaporation is carried on. The moisture thus charged upon the atmosphere by day, is precipitated during the cooler hours of night in fog, mist, or rain.

In summer, the prevailing wind of the coast is from the north-west, thus following the general direction of the shore-line. It naturally carries the sea-vapor inland; but the first obstacle encountered by these masses of vapor is a range of mountains high enough to cause, by their altitude and consequent lower temperature, the precipitation of a large amount of moisture upon this seaward slope. Still, a considerable portion of moisture is carried over this first range, and through the gaps in the mountains, and falls in rain or mist upon the level prairie country beyond. Not so, however, with the second, or Cascade Range. These mountains, by their height, intercept the sea-fog completely; and while great masses of vapor overhang their western slopes, on their eastern foot-hills and the rolling prairies beyond not a drop of dew has fallen. This is the explanation of the difference in climate, as regards dryness and moisture, between Eastern and Western Oregon and Washington. All other differences depend on altitude and local circumstances.

Notwithstanding the great amount of moisture precipitated upon the country west of the Cascades, the general climate may be said to be drier than on the Atlantic Coast. The atmosphere does not seem to hold moisture, and even in rainy weather its drying qualities are remarkable. Taken altogether, the stormy days in this part of Oregon and Washington are not more numerous than in the Atlantic States; but the rainy days are, because all the storms here are rain, with rare exceptions. The autumn rains commence,