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North Pacific Coast 152

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NORTH PACIFIC COAST 152. The mountain region of the Pacific Coast.—There is not so much plain near the Pacific coast as there is along the Atlantic coast. In many places the coast ranges rise steeply from the Pacific shore. On Fig. 14, examine the mountain system from the southern end of Lower California to the Peninsula of Alaska, and that from Labrador to the Southern Appalachians. Which moun tain system has the better natural highways through it? Compare them in height. Lo cate the Sierra Nevada, the Cascade Moun tains, the Coast Ranges. How long is the mountainous peninsula of Lower California? How far is it from Mexico to Canada? from Washington State to Alaska? How long is the south coast of Alaska? These four sections combine to make this long mountain region.

North of the Columbia Basin, the Cascade Moun tains and the Rocky Moun tains join and form one great mountain mass that continues into Alaska, and finally extends across the sea as the Aleutian Islands. These islands are a string of volcanoes whose tops stick out of the sea.

153. Climate of the Pacific mountains.—As we have crossed the continent in the course of our study we have seen that the weather is very different in different places. We saw that western Texas has so little rain that the land is good only for pasture, while eastern Texas has so much rain that it is a good place for corn, cotton, and other moist land crops, even for rice, the grain that grows in the water. We found beautiful streams flowing out of the forested Rocky Mountains, and we also found Death Valley, where it is so dry that men die of thirst. How much rain falls in Death Valley in a year? (Fig. 158.) The Pacific mountains also have many kinds of climate, and to understand how this happens we must study more about rainfall.

154. The cyclone and the rain.—What do cyclones do for the western parts of our country? When a cyclone crosses the Pacific Mountains and the plateaus near them, the storm path usually stays near the Canadian boundary. What happens when a cyclone center travels from the Pacific across Washington, Idaho, Montana, and South Dakota? In the United States the wind blows toward this storm center from the west and south. After the wind

the Pacific Ocean, it strikes the west side of the mountains near the coast and heavy rain falls on the windward slope of each range.

155. Water vapor.—It is interesting to know why rain falls when the wind crosses a mountain. There is always water in the air in the invisible form called vapor. Although the air may seem clear, and we cannot see the tiny particles of water vapor, they are there, as there is water in a damp sponge after you have squeezed it.

We have all seen wet clothes hung on a line to dry. The air takes the water out of the clothes, as a sponge or a cloth takes up water into which it has been dropped. If you squeeze the sponge or the cloth, the water comes out.

The same thing happens to water that is held in the air, but the way to squeeze the air is to make it cooler. The blacksmith or the plumber will tell you that if you heat a piece of metal it becomes larger (expands), and if you cool it it becomes smaller (contracts). So it is with air. If we heat it, it expands and leaves more room between the air particles for water vapor to slip into. That is why warm air dries clothes faster than does cool air. The air in a room on a hot summer day when the thermometer is 90° F. will hold several times as much water vapor as it does on a winter day when the temperature is only 30°.

156. a glass of ice water we can see how dew is squeezed out of the air. Watch the little drops of water form (con dense) on the outside of a glass of ice water in a warm room. Why do they appear? It is because the glass of ice water cools a little of the air that surrounds it, and when the air near the glass becomes cool, it can not hold as much water vapor as it could when it was warm, so the vapor condenses and forms dewdrops, or drops of water, on the cool glass. The condensed vapor or dew drops cling to the outside of the glass, and we can see them become larger and larger until at last they run down the side of the glass.

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