Westward of the Cascade summits the commercial forest of to-day extends down from an elevation of about 3,500 feet. Intercepted by these heights, the moisture-laden clouds are emptied on the crest of the range. Eastward, the effects of decreasing precipitation are shown both in species and in density. Tamarack, white fir and pines climb higher on these warmer slopes. Along the base of the mountains, and beyond low passes where strong west winds drive saturated clouds out over level reaches, western yellow pine (_Pinus ponderosa_) becomes almost the only tree. Over miles of level lava flow, along the upper Deschutes, this species forms a great forest bounded on the east by rolling sage-brush plains that stretch southward to the Nevada deserts. Beyond the Deschutes drainage, where spurs of the Blue mountains rise to the levels of clouds and moisture, the forest again covers the hills, spreading far to the east until it disappears again in the broad, treeless valley of Snake river. North of the Columbia the story is the same. From the lower slopes of Mt. Adams great rolling bunch-grass downs and prairies reach far eastward. Here and there, over these drier stretches, stand single trees or clusters of western juniper (_Juniperus occidentalis_). [Illustration: Fifty-year-old Hemlock growing on Cedar log. The latter, which was centuries old before it matured and fell, was still sound enough to yield many thousand shingles.] But on the west slope of the Cascades, and over the Coast range, the great forests spread in unbroken array, save where wide valleys have been cleared by man or hillsides stripped by fire. Here, in the land of warm sea winds and abundant moisture, the famous Douglas fir (_Pseudotsuga taxifolia_), Pacific red cedar (_Thuja plicata_) and tideland spruce (_Picea sitchensis_) attain their greatest development. These are the monarchs of the matchless Northwestern forests, to which the markets of the world are looking more and more as the lines of exhausted supply draw closer. [Illustration: Sawyers preparing to "fall" a large Tideland Spruce.] Douglas fir recalls by its name one of the heroes of science, David Douglas, a Scotch naturalist who explored these forests nearly ninety years ago, and discovered not only this particular giant of the woods, but also the great sugar pine and many other fine trees and plants. As a pioneer botanist, searching the forest, Douglas presented a surprising spectacle to the Indians. "The Man of Grass" they called him, when they came to understand that he was not bent on killing the fur-bearing animals for the profit to be had from their pelts. [Illustration: Sugar Pine, Douglas Fir, and Yellow Pine.]