英語美文朗讀

　　英語朗讀通過朗讀提高學生對英語的記憶,同時還加強了學生對語感的培養,提高口語水平。下面是小編帶來的，歡迎閱讀!

　　Cohesion-tension Theory

　　Atmospheric pressure can support a column of water up to 10 meters high. But plants can move water much higher; the sequoia tree can pump water to its very top more than 100 meters above the ground. Until the end of the nineteenth century, the movement of water in trees and other tall plants was a mystery. Some botanists hypothesized that the living cells of plants acted as pumps. But many experiments demonstrated that the stems of plants in which all the cells are killed can still move water to appreciable heights. Other explanations for the movement of water in plants have been based on root pressure, a push on the water from the roots at the bottom of the plant. But root pressure is not nearly great enough to push water to the tops of tall trees. Furthermore, the conifers, which are among the tallest trees, have unusually low root pressures.

　　If water is not pumped to the top of a tall tree, and if it is not pushed to the top of a tall tree, then we may ask: how does it get there According to the currently accepted cohesion-tension theory, water is pulled there. The pull on a rising column of water in a plant results from the evaporation of water at the top of the plant. As water is lost from the surface of the leaves, a negative pressure, or tension, is created. The evaporated water is replaced by water moving from inside the plant in unbroken columns that extend from the top of a plant to its roots. The same forces that create surface tension in any sample of water are responsible for the maintenance of these unbroken columns of water. When water is confined in tubes of very small bore, the forces of cohesion ***the attraction between water molecules*** are so great that the strength of a column of water compares with the strength of a steel wire of the same diameter. This cohesive strength permits columns of water to be pulled to great heights without being broken.

　　內聚壓力理論

　　大氣壓能夠支援10米高的水柱，但植物可將水送得更高。美洲紅杉就能把水泵到地面以上100多米高的樹頂。直到19世紀末，水在樹木和其它高大植物中的輸送還是一個謎。一些植物學家假定植物中的活細胞充當了水泵的角色。但許多實驗表明細胞都已死亡的植物莖幹仍能將水輸送到相當可觀的高度。對於植物中輸送水的其它解釋都基於根壓--植物底端的根對水的推動。但根壓完全不足以將水推到樹頂。況且，最高樹木中的松柏只有很低的根壓。

　　如果水不是被泵到高樹的樹頂，也不是被推到樹頂，那麼我們會問：它是怎樣到達樹頂的呢?根據目前為人們所接受的內聚壓力的理論，水是被拉到上面去的。一株植物中作用於一個正在升高的水柱之上的拉力來自該植物頂部水的蒸發。由於水從葉子表面喪失，一個負壓力，或張力就得以產生。蒸發出去的水被植物裡流動的水代替。這些水形成水柱從植物頂端一直延伸到根部。在任何水樣中造成表面張力的力支援著這些不斷的水柱。當水被限制在內徑很小的管道中時，內聚壓力***水分子之間的相互吸引力***是如此之大以致一支水柱的強度相當於一根直徑相同的鋼絲的強度。這種內聚壓力使得水柱被拉到非常高的地方而不會斷裂。

　　Icebergs

　　Icebergs are among nature’s most spectacular creations, and yet most people have never seen one. A vague air of mystery envelops them. They come into being ----- somewhere ----- in faraway, frigid waters, amid thunderous noise and splashing turbulence, which in most cases no one hears or sees. They exist only a short time and then slowly waste away just as unnoticed.

　　Objects of sheerest beauty they have been called. Appearing in an endless variety of shapes, they may be dazzlingly white, or they may be glassy blue, green or purple, tinted faintly of in darker hues. They are graceful, stately, inspiring ----- in calm, sunlight seas.

　　But they are also called frightening and dangerous, and that they are ---- in the night, in the fog, and in storms. Even in clear weather one is wise to stay a safe distance away from them. Most of their bulk is hidden below the water, so their underwater parts may extend out far beyond the visible top. Also, they may roll over unexpectedly, churning the waters around them.

　　Icebergs are parts of glaciers that break off, drift into the water, float about awhile, and finally melt. Icebergs afloat today are made of snowflakes that have fallen over long ages of time. They embody snows that drifted down hundreds, or many thousands, or in some cases maybe a million years ago. The snows fell in polar regions and on cold mountains, where they melted only a little or not at all, and so collected to great depths over the years and centuries.

　　As each year’s snow accumulation lay on the surface, evaporation and melting caused the snowflakes slowly to lose their feathery points and become tiny grains of ice. When new snow fell on top of the old, it too turned to icy grains. So blankets of snow and ice grains mounted layer upon layer and were of such great thickness that the weight of the upper layers compressed the lower ones. With time and pressure from above, the many small ice grains joined and changed to larger crystals, and eventually the deeper crystals merged into a solid mass of ice.

　　冰山

　　冰山是大自然最壯觀的創造之一，但大多數人卻從未看到過冰山，一種朦朧神祕的氣氛籠罩著它們。冰山形成於久遠的、寒冷的水體中，而且伴隨著雷聲轟鳴般的嘈雜和水花洶湧的風暴，但卻無人耳聞目睹。冰山僅存在短短的一段時間就慢慢地悄無聲息地融化掉。

　　冰山具有最純粹的美，人們如是說。冰山呈現出千姿百態，可能白得耀眼，或者是閃耀著藍色、綠色或紫色的玻璃般的光芒，或濃或淡。它們在平靜的陽光照耀的海水中顯得優雅堂皇，令人浮想聯翩。

　　但是人們亦把冰山稱為恐怖的和危險的。它們的確如此--在夜間，霧天和風暴肆虐時。即便是在晴朗的天氣裡，與它們保持一段安全距離也是明智的。冰山的大部分體積穩藏於水下，因此其水下部分的伸展遠遠超過可見的頂部。冰山也可能出人意料地翻滾，劇烈地攪動周圍的水體。

　　冰山是冰川的一部分，從冰川斷裂漂流進水中，一段時間後融化。今天的冰山由多年前降落的雪花形成。它們的體內是數百年，或數千年，有時甚至是數百萬年前的降雪。這些雪花落在極地或寒冷的山上，僅有少量融化或根本不融化，這樣經過許多年或許多世紀後積累了巨大的深度。

　　由於每年的雪花積累在表面之上，蒸發和融化使得雪花慢慢失去其羽狀尖端而變成微小的冰粒。當新的雪花降落到舊的表面上，也變成了冰粒。因而雪花覆蓋層和冰粒層層堆積起來直到如此之大的厚度以致較上層的重量壓縮較下層。在時間和壓力的作用下，許多小冰粒結合到一起變成更大的晶體，最終較底層的晶體合併成龐大而堅固的冰塊。

　　British Columbia

　　British Columbia is the third largest Canadian provinces, both in area and population. It is nearly 1.5 times as large as Texas, and extends 800 miles ***1,280km*** north from the United States border. It includes Canada’s entire west coast and the islands just off the coast.

　　Most of British Columbia is mountainous, with long rugged ranges running north and south. Even the coastal islands are the remains of a mountain range that existed thousands of years ago. During the last Ice Age, this range was scoured by glaciers until most of it was beneath the sea. Its peaks now show as islands scattered along the coast.

　　The southwestern coastal region has a humid mild marine climate. Sea winds that blow inland from the west are warmed by a current of warm water that flows through the Pacific Ocean. As a result, winter temperatures average above freezing and summers are mild. These warm western winds also carry moisture from the ocean.

　　Inland from the coast, the winds from the Pacific meet the mountain barriers of the coastal ranges and the Rocky Mountains. As they rise to cross the mountains, the winds are cooled, and their moisture begins to fall as rain. On some of the western slopes almost 200 inches ***500cm*** of rain fall each year.

　　More than half of British Columbia is heavily forested. On mountain slopes that receive plentiful rainfall, huge Douglas firs rise in towering columns. These forest giants often grow to be as much as 300 feet***90m*** tall, with diameters up to 10 feet***3m***. More lumber is produced from these trees than from any other kind of tree in North America. Hemlock, red cedar, and balsam fir are among the other trees found in British Columbia.

　　英屬哥倫比亞

　　英屬哥倫比亞是加拿大的第三大省，無論是面積還是人口都是如此。它幾乎是德克薩斯的1.5倍，從美國邊境一直向北延伸了800英里***1，280公里***。它包括了加拿大整個西海岸及附近島嶼。

　　大部分英屬哥倫比亞多山巒。綿長而粗獷的山脈貫通南北。甚至那些沿海的島嶼都是那些存在於千萬年前的山脈的遺蹟。在上一個冰河時期，這些山脈被冰河沖刷侵蝕，直到大部分山脈被淹沒在海中。它們的峰頂顯現為沿著海岸散佈的島嶼。

　　西南海岸地區有著潮溼溫和的海洋性氣候。從太平洋來的溫暖的洋流使得從西吹過內陸的海風變得溫暖。因此這兒冬天平均氣溫在零上而且夏天也不會酷熱。這些溫暖的西風同樣也從海洋帶來了溼氣。

　　來自太平洋的、從海岸向內陸的風遇到海岸山脈和落基山脈這些山脈屏障。當氣流升高跨越這些山脈時，風的溫度就降低了，風中的水分形成降雨。在一些朝西山坡區域每年大約有200英寸***500釐米***的降水。

　　大部分英屬哥倫比亞密佈著森林。在有充足降水的斜坡，巨大的道格拉斯樅樹高聳入雲。這些森林巨人常常長到高達300英尺***90米***，直徑粗達10英尺***3米***。這些樹產出了比北美其他任何樹都多的木材。鐵杉、紅香椿、香脂冷杉樅都是發現於英屬哥倫比亞的其它樹種。