Page:The Pacific Monthly volumes 1-3.djvu/26

 grounds (as well as the fishing-grounds) for vast numbers of fish. The streams or currents of the ocean along the northwest coast are dominated by the effects of the Japanese stream, the great ocean current of the Pacific, which, having its rise in the warm regions of the tropics, flows past the coast of Japan, and, crossing over, loses itself on the American shores. The course and effect of this stream is very similar to the well-known Gulf stream of the Atlantic. It keeps the temperature of the ocean at nearly a constant degree of warmth throughout the year, and we shall see that it has the effect of maintaining a very modified and mild winter climate in comparatively high latitudes.

The ocean currents, however, are changed by the force and direction of the prevailing winds on this coast. For nearly half of the year, northwest winds prevail along the whole coast, while during the winter months the winds come from the southeast and southwest. The summer winds, far off the coast, are the trade winds, and blow from the southwest, gradually shifting, as the coast is approached, to the northwest. In winter the southerly winds pile up the waters along the coast, and, flowing off, produce a strong current to the northward, as is seen by the frequent presence of redwood logs cast up on the shores, a tree which hardly appears north of the California line. The prevailing winds of summer, blowing from off the ocean, maintain a very equable degree of temperature over the land, as far as their influence reaches, a temperature entirely controlled by the effects of the Japan stream. The polar current of cold, Arctic waters, flowing down through Behring straits, owing to the difference in specific gravity of warm and cold water, settles down and flows underneath the warm equatorial waters.

The winds blowing over the warm surface waters absorb the radiated heat and maintain the high annual mean temperature over our land, which we enjoy. Were it not for the great modification in climate produced by the Japan stream, the limit of perpetual snow would reach far down the slopes of the Cascade mountains, and the glaciers of Mount Hood and Mount Adams probably reach to the Columbia river. The effects of these winds are felt along the coast as far inland as the Cascade mountains.

East of that great barrier, the summers are warmer and the winters colder than on the west. The climate in other respects is very dissimilar, rain being more prevalent on the west, and snow on the east side of these mountains.

The geological features of the northwest coast are well marked. The eozoic formation is found in the Coast range and in the Blue mountains — but the greatest exemplification of any geologic age in the Northwest is the volcanic.

The Sierra Nevada and Cascade range was elevated at the close of the Jurassic period, but not to its present height. At the end of the Miocene period, simultaneously with the elevation of the Coast range, the Cascade and Sierra Nevada mountains were lifted up to their present great elevation, and, under the tremendous pressure, seem to have been rent and fissured along the entire crest from Middle California to the far North in British America. During this elevation took place the most stupendous exhibition of volcanic and eruptive energy of any age or part of the world, great floods of liquid lava and basalt pouring from the Cascade range, covering nearly the whole of Oregon, Washington and Idaho, and extending into Nevada, California and British Columbia, and into the ocean. This great deposit flowed over the country in waves and sheets, filling the beds of rivers and creeks to a depth of 2,000 to 4,000 feet, and utterly destroying all life. The gloomy canyon of the Snake river is a most striking illustration of the depth of the lava flow, where may be seen along its terraced sides the thickness of the successive sheets. The bottom of this lava flow is an unknown depth below the sea level, as can be seen in the great ocean capes and in the bluffs along the Columbia river. Towards the close of this eruption, the vents of the imprisoned fires became confined to the points known as Mounts Shasta, Hood, Rainier, etc., from which liquid lava, scoriae, pumice and ashes continued to be emitted for a long period, building up their cones to a height probably far above their present altitude. The action of glaciers and melting ice is believed to have worn away the height of