27） Scientific Theories（科學理論） In science, a theory is a reasonable explanation of observed events that
are related. A theory often involves an imaginary model that helps
scientists picture the way an observed event could be produced. A good
example of this is found in the kinetic molecular theory, in which gases
are pictured as being made up of many small particles that are in constant
motion.
A useful theory, in addition to explaining past observations, helps to
predict events that have not as yet been observed. After a theory has been
publicized, scientists design experiments to test the theory. If
observations confirm the scientists' predictions, the theory is
supported. If observations do not confirm the predictions, the scientists
must search further. There may be a fault in the experiment, or the theory
may have to be revised or rejected. 
Science involves imagination and creative thinking as well as collecting
information and performing experiments. Facts by themselves are not
science. As the mathematician Jules Henri Poincare said,"Science is built
with facts just as a house is built with bricks, but a collection of facts
cannot be called science any more than a pile of bricks can be called
a house." Most scientists start an investigation by finding out what other
scientists have learned about a particular problem. After known facts have
been gathered, the scientist comes to the part of the investigation that
requires considerable imagination. Possible solutions to the problem are
formulated. These possible solutions are called hypotheses.
In a way, any hypothesis is a leap into the unknown. It extends the
scientist's thinking beyond the known facts. The scientist plans
experiments, performs calculations, and makes observations to test
hypotheses. Without hypothesis, further investigation lacks purpose and
direction. When hypotheses are confirmed, they are incorporated into
theories.
在科學中，理論是對所觀察到的相關事件的合理解釋。 理論通常包含一個虛構的模型，
這個模型幫助科學家構想所觀察到的事件是如何發生的。 分子運動理論便是我們能找到的 一個很好的例子。
在這個理論中，氣體被描繪成由許多不斷運動的小顆粒組成。 一個有用 的理論，除了能夠解釋過去的觀測，還有助于預測那些未被觀測到的事件。 一個理論公開
后，科學家們設計實驗來檢驗這個理論。 如果觀察證實了科學家的預言，這個理論則得到 了驗證。 如果觀察不能證實科學家的預言，科學家就必須進一步的研究。
或許是實驗存在 錯誤，或許是這個理論必須被修改或拋棄。 科學家除了收集信息和操作實驗外還需要想象 能力和創/造性思維。 事實本身并不是科學。
正如數學家喬斯?亨利?波恩克爾所說："科 學建立在事實之上，就像房子用磚砌成一樣。 但事實的收集不能被稱作科學，就像一堆磚 不能被叫作房子一樣。
"多數科學家通過找出別的科學家在一個特定問題上的所知來開始研 究。在收集了已知事實之后，科學家開始了研究中需要相當想像力的部分。 他們爾后擬訂
對這個問題的可行的解決方法。這些可行的解決方式被稱為假設。 在某種意義上，任何假
設都是向未知的跳躍。它使科學家的思維超越已知事實。科學家計劃實驗、計算、觀測以檢 驗假定。若沒有假設，進一步的研究便缺乏目的和方向。
當假設被證實了，就成為理論的 一部分。
28 Changing Roles of Public Education（公共教育的角色變化）One of the most important social developments that helped to make
possible a shift in thinking about the role of public education was the
effect of the baby boom of the 1950's and
1960's on the schools. In the 1920's, but especially in the Depression
conditions of the 1930's, the United States experienced a declining birth
rate -- every thousand women aged fifteen to forty-four gave birth to about
118 live children in 1920，89.2 in 1930，75.8 in 1936, and 80 in
1940. With the growing prosperity brought on by the Second World War and
the economic boom that followed it young people married and established
households earlier and began to raise larger families than had their
predecessors during the Depression. Birth rates rose to 102 per thousand
in 1946, 106.2 in 1950, and 118 in 1955. Although economics was probably
the most important determinant, it is not the only explanation for the
baby boom. The increased value placed on the idea of the family also helps
to explain this rise in birth rates. The baby boomers began streaming into
the first grade by the mid 1940's and became a flood by 1950. The public
school system suddenly found itself overtaxed. While the number of
schoolchildren rose because of wartime and postwar conditions, these same
conditions made the schools even less prepared to cope with the flood. The
wartime economy meant that few new schools were built between 1940 and
1945. Moreover, during the war and in the boom times that followed, large
numbers of teachers left their profession for better-paying jobs elsewhere
in the economy.
Therefore in the 1950's and 1960's, the baby boom hit an antiquated and
inadequate school system. Consequently, the "custodial rhetoric"of the
1930's and early 1940's no longer made sense that is, keeping youths aged
sixteen and older out of the labor market by keeping them in school could
no longer be a high priority for an institution unable to find space
and staff to teach younger children aged five to sixteen. With the baby
boom, the focus of educators and of laymen interested in education
inevitably turned toward the lower grades and back to basic academic
skills and discipline. The system no longer had much interest in offering
nontraditional, new, and extra services to older youths. 
一項重要的、有可能促使人們對公共教育的角色的看法發生轉變的社會發展是本世紀五六十年代的生育高峰對學校的影響。 在 20 年代，尤其是在 30 年代后的大蕭條中，美國經 歷了一次出生率的下降--1920 年每千名年齡在 15歲至 45 歲的婦女生下大約 118 個存活嬰兒，1930 年 89.2 個，1936 年 75.8 個，1940 年 80 個。 隨著二戰帶來的持續繁榮以及隨之而來的經濟增長，年輕人比大蕭條中的同齡人更早地結婚成家，而且比前輩養育更大的家庭。
1946 年出生率上升到 102%，1950 年達 106%，1955 年達 118%。 對于生育高峰，經濟有可
能是最重要的決定因素，但它并不是唯一的解釋。 不斷受到重視的家庭觀念也有助于解釋 出生率的上升。 到 40
年代中期為止，這些生育高峰出生的孩子們開始源源不斷地進入小學 一年級。 到了 1950 年，就形成了一股洪流。 公共教育系統突然感到不堪重負了。
由于戰時和戰后的狀況，使得學齡兒童人數增加，這些狀況使得學校面對這股洪流更加措手不及。 戰時經濟意味著在 1940 年到 1950 年間幾乎沒有建立新學校。 而且，在戰時和隨后的經濟 增長時期，大量的教師離開崗位去別處從事報酬更為優厚的工作。 因此，在五六十年代，生育高峰沖擊著陳舊而不完備的學校體系。 這樣一來，30 年代以及 40 年代早期，"監護理 論"就不再有意義了。 也就是說，通過使 16 歲以上的年輕人留在學校不進入勞動力市場的 做法再也不是教育機構的優先考慮了。 因為教育機構不再能找到場地和教師來教育那些更 小的 5-16 歲的孩子。 隨著生育高峰，教育者和圈外人士對教育的興趣和焦點，不可避免地 轉向了更低的年級和基礎的學術技能和學科上。這個系統不再有濃厚的興趣給較年長的年 輕人提供非傳統的新式的和額外的服務。
29） Telecommuting （電子交通） Telecommuting -- substituting the computer for the trip to the job -- has
been hailed as a solution to all kinds of problems related to office work.
For workers it promises freedom from the office, less time wasted in
traffic, and help with child-care conflicts. For management, telecommuting
helps keep high performers on board, minimizes tardiness and absenteeism
by eliminating commutes, allows periods of solitude for high-concentration
tasks, and provides scheduling flexibility.
In some areas, such as Southern California and Seattle, Washington, local
governments are encouraging companies to start telecommuting programs in
order to reduce rush-hour congestion and improve air quality.
But these benefits do not come easily. Making a telecommuting program
work requires careful planning and an understanding of the differences
between telecommuting realities and popular images.
Many workers are seduced by rosy illusions of life as a
telecommuter. A computer programmer from New York City moves to the
tranquil Adirondack Mountains and stays in contact with her office via
computer. A manager comes in to his office three days a week and works at
home the other two. An accountant stays home to care for her sick child;
she hooks up her telephone modem connections and does office work between
calls to the doctor.
These are powerful images, but they are a limited reflection of
reality. Telecommuting workers soon learn that it is almost impossible to
concentrate on work and care for a young child
at the same time. Before a certain age, young children cannot recognize,
much less respect, the necessary boundaries between work and family.
Additional child support is necessary if the parent is to get any work
done.
Management too must separate the myth from the reality. Although the media
has paid a great deal of attention to telecommuting in most cases
it is the employee's situation, not the availability of technology
that precipitates a telecommuting arrangement.
That is partly why, despite the widespread press coverage, the number of
companies with work-at-home programs or policy guidelines remains small.
電子交通--用電腦取代上班的往返--作為對各種各樣的辦公室工作問題的解決辦法已受 到了歡迎。
對工作者來說，它承諾不受辦公室的約束，更少的時間浪費在交通上和有助于 解決照看小孩的矛盾。
對管理者來說，電子交通有助于挽留高效率的工作者，通過省去辦 公室與家之間的來回往返，大大減少工作拖拉和曠工，給予管理者獨處的時間來完成需要高
度集中精神的任務，為管理者提供靈活的時間安排。 在一些地區，如南加利福尼亞和西雅
圖、華盛頓，地方政府鼓勵公司開始電子交通計劃以減少交通高峰時的塞車和提高空氣質量。 但這些益處也來之不易。
要使電子交通成功需要仔細的計劃并且理解電子交通的現實狀況 和流行的想象之間的區別。 許多工作者被電子交通的美好幻想所迷惑。 一位電腦程序設計
員從紐約市搬到了寧靜的阿第倫達克山，用電腦保持與她辦公室之間的聯系。 一位經理一
周三天到辦公室，其他兩天在家工作；一位會計師在家照顧她生病的孩子，接通電話調制解 調器的接頭，在同醫生通話之余完成辦公室工作。
這些是很有震撼力的情景，但也是對現 實有限的反映。 電子交通者很快發現在同一時間專注工作和照看小孩幾乎是不可能的。 在
某個年齡之前，小孩子不可能意識到，更不可能尊重工作與家庭之間的界限。 如果家長要 完成工作，就必須另外照看小孩。 管理階層必須把現實同神話分開。
雖然傳媒對電子交通 投入了極大的關注，但在很大程度上，是員工的實際情況而不是技術的可能性促成電子交通 的安排。
這就是為什么盡管有廣泛的報導，具有在家工作項目或行動綱領的公司數目依然 很少的部分原因。
30） The Origin of Refrigerators（冰箱的由來） By the mid-nineteenth century, the term"icebox"had entered the American
language, but ice was still only beginning to affect the diet of ordinary
citizens in the United States. The ice trade grew with the growth of
cities. Ice was used in hotels, taverns, and hospitals, and by some
forward-looking city dealers in fresh meat, fresh fish, and
butter. After the Civil War
(1861-1865), as ice was used to refrigerate freight cars, it also came into
household use. Even before 1880, half the ice sold in New York,
Philadelphia, and Baltimore, and one-third of that sold in Boston and
Chicago, went to families for their own use. This had become possible
because a new household convenience, the icebox, a precursor of the
modern refrigerator, had been invented.
Making an efficient icebox was not as easy as we might now suppose. In the
early nineteenth century, the knowledge of the physics of heat, which was
essential to a science of refrigeration, was rudimentary. The commonsense
notion that the best icebox was one that prevented the ice from melting was
of course mistaken, for it was the melting of the ice that performed the
cooling. Nevertheless, early efforts to economize ice included wrapping the
ice in blankets, which kept
the ice from doing its job. Not until near the end of the nineteenth
century did inventors achieve the delicate balance of insulation and
circulation needed for an efficient icebox.
But as early as 1803, an ingenious Maryland farmer, Thomas Moore, had been
on the right track. He owned a farm about twenty miles outside the city of
Washington, for which the village of Georgetown was the market center. When
he used an icebox of his own design to transport his butter to market, he
found that customers would pass up the rapidly melting stuff in the tubs of
his competitors to pay a premium price for his butter, still fresh and hard
in neat, one-pound bricks. One advantage of his icebox, more explained, was
that farmers would no longer have to travel to market at night in order to
keep their produce cool. 
直到 19 世紀中期，"冰箱"這個名詞才進入了美國語言，但冰僅僅只是開始影響美國普 通市民的飲食。 冰的買賣隨著城市的發展而發展。
冰被用在旅館、酒館、醫院以及被一些 有眼光的城市商人用于肉、魚和黃油的保鮮。 內戰(1861-1865)之后，冰被用于冷藏貨車， 同時也進入了民用。
甚至在 1880 年前，半數在紐約、費城和巴爾的摩銷售的冰，三分之一
在波士頓和芝加哥銷售的冰進入家庭使用，因為一種新的家庭設備，冰箱，即現代冰箱的前 身，被發明了。 制造一臺有效率的冰箱不像我們想象的那么簡單。
19 世紀早期，關于對 冷藏科學至關重要的熱物理知識是很淺陋的。 認為最好的冰箱應該防止冰的融化這樣一個
普遍的觀點顯然是錯誤的，因為正是冰的融化起了制冷作用。 早期為節省冰的努力，包括 用毯子把冰包起來，使得冰不能發揮它的作用。 直到近 19
世紀末，發明家們才成功地找到 有效率的冰箱所需要的精確的隔熱和循環的精確平衡。 但早在 1803 年，一位有發明天才的
馬里蘭農場主，托馬斯?莫爾，找到了正確方法。 他擁有一個農場，離華盛頓約 20 英里， 那里的喬治鎮村莊是集市中心。
當他用自己設計的冰箱運送黃油去市場時，他發現顧客們 會走過裝在競爭者桶里那些迅速融化的黃油而給他比市價更高的價格買他仍然新鮮堅硬，整
齊地切成一磅一塊的黃油。 莫爾說他的冰箱的一個好處是使得農民們不必在夜里上路去市 場以保持他們產品的低溫。
31） British Columbia（英屬哥倫比亞） British Columbia is the third largest Canadian province, 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于千萬年前的山脈的遺跡。 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布的島嶼。 西南 海岸地區有著潮濕溫和的海洋性氣候。 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 海洋帶來了濕氣。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 厘米)的降水。 大部分英屬哥倫比亞密布著森林。 在有 充足降水的斜坡，巨大的道格拉斯樅樹高聳入云。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于英屬哥倫比亞的其它樹種。
32） Botany（植物學）  Botany, the study of plants, occupies a peculiar position in the history of
human knowledge. For many thousands of years it was the one
field of awareness about which humans had anything more than the
vaguest of insights. It is impossible to know today just what our Stone Age
ancestors knew about plants, but from what we can observe of preindustrial
societies that still exist a detailed learning of plants and their
properties must be extremely ancient. This is logical. Plants are the
basis of the food pyramid for all living things even for other plants. They
have always been enormously important to the welfare of people not only for
food, but also for clothing, weapons, tools, dyes, medicines, shelter, and
a great many other purposes. Tribes living today in the jungles of the
Amazon recognize literally hundreds of plants and know many properties of
each. To them, botany, as such, has no name and is probably not even
recognized as a special branch of "knowledge"at all.
Unfortunately, the more industrialized we become the farther away we move
from direct contact with plants, and the less distinct our knowledge of
botany grows. Yet everyone comes unconsciously on an amazing amount of
botanical knowledge, and few people will fail to recognize a rose,
an apple, or an orchid. When our Neolithic ancestors, living in the Middle
East about 10, 000 years ago, discovered that certain grasses could be
harvested and their seeds planted for richer yields the next season the
first great step in a new association of plants and humans was taken.
Grains were discovered and from them flowed the marvel of agriculture:
cultivated crops. From then on, humans would increasingly take their living
from the controlled production of a few plants, rather than getting a
little here and a little there from many varieties that grew wild - and the
accumulated knowledge of tens of thousands of years of experience and
intimacy with plants in the wild would begin to fade away.
植物學，即對植物的研究，在人類知識的歷史中占據了特殊的地位。 這是人類幾千年來超越模糊的認知而真正有所了解的領域之一。我們今天不可能知道新石器時代的祖先們 對植物到底了解多少，但我們在至今仍存在的前工業化社會觀察到：人類對植物及其特性的 詳細了解應該是非常古老的。
這是理所當然的。 植物是其他生物甚至其他植物食物金字塔 的基礎。 它們對人們的生活至關重要，不僅在食物上，而且在衣物、武器、工具、染料、藥物、住所和許許多多其他的用途上。 至今仍生活在亞馬遜河叢林中的部落確實能夠辨識 幾百種植物并知道每一種的許多特性。對他們來說，植物學沒有專門的名稱，甚至可能根 本未被認為是一種專門知識。 不幸的是，工業化的程度越高，我們距直接與植物接觸就越 遠，我們的植物學知識的增加也就越微不足道。 然而每個人在不知不覺中擁有大量的植物學知識，很少有人認不出玫瑰、蘋果或蘭花。
大約一萬年前居住在中東的新時代的祖先們 發現某些草能被收獲，它們的種子下一季耕種會收獲更多時，人類就邁出了人和植物之間的 新關系第一大步。 谷子被發現后，農業的奇跡從此誕生：這就是可栽培的谷物。從那時起， 人類越來越依賴少數可控制的作物生存，而不再是從眾多的野生種類中這里獲取一點，那里獲取一點。這樣在千萬年中對于野生植物的經驗和密切聯系中積累起來的知識就開始消失 了。
33） Plankton（浮游生物）Scattered through the seas of the world are billions of tons of small
plants and animals called plankton. Most of these plants and animals are
too small for the human eye to see. They drift about lazily with the
currents, providing a basic food for many larger animals.
Plankton has been described as the equivalent of the grasses that grow on
the dry land continents, and the comparison is an appropriate one. In
potential food value, however, plankton far outweighs that of the land
grasses. One scientist has estimated that while grasses of the world
produce about 49 billion tons of valuable carbohydrates each year, the
sea's plankton generates more than twice as much.
Despite its enormous food potential, little effect was made until recently
to farm plankton as we farm grasses on land. Now marine scientists have at
last begun to study this possibility, especially as the sea's resources
loom even more important as a means of feeding an expanding world
population.
No one yet has seriously suggested that "planktonburgers" may soon become
popular around the world. As a possible farmed supplementary food
source, however, plankton is gaining considerable interest among marine
scientists.
One type of plankton that seems to have great harvest possibilities is a
tiny shrimplike creature called krill. Growing to two or three inches long,
krill provide the major food for the great blue whale, the largest animal
ever inhabit the Earth. Realizing that this whale may grow to
100 feet and weigh 150 tons at maturity, it is not surprising that each one
devours more than one ton of krill daily. 
數十億噸的被稱為"浮游生物"的小動物、植物散布在世界的海洋中。 這些小 的動、植物大多太小而難以被人眼看到。
它們隨波逐流，為許多較大的動物提供了基本的 食物。 浮游生物曾被描述為生長在大陸陸地上的各種草類的海洋對應物。 這種比喻是恰當的。 然而就潛在的食物價值而言，浮游生物遠勝于草類。 一位科學家曾經估計，世界上的 草類每年生產大約 490
億噸有用的碳水化合物，而海洋里的浮游生物每年生產的碳水化合物 多于此數的兩倍。 盡管浮游生物具備巨大的食物潛能，但直到最近人們還很少象種植草類那樣付出努力養殖浮游生物。 現在，海洋科學家們至少已開始研究這種可能性。 全球人口 不斷擴張，海洋資源作為食品的重要性日益突出。 現在還沒有人認真說過"浮游生物漢堡" 會很快在世界上流行起來。 然而，作為一種可能養殖的補充性食物資源，浮游生物正引起 了海洋科學家們相當大的興趣。 一種似乎具有很大收獲可能性的微小的蝦狀浮游生物被稱 為鱗蝦。 鱗蝦長至 2～3 英寸長時即成為地球上曾居住過的最大動物--藍鯨的主要食物。成熟的藍鯨可以達到 100 英尺長，150 噸重，所以每頭鯨每天吞食 1 噸多的鱗蝦一點也不讓人 吃驚。
34） Raising Oysters （飼養牡蠣） In the past oysters were raised in much the same way as dirt farmers raised
tomatoes - by transplanting them. First, farmers selected the oyster
bed, cleared the bottom of old shells and other debris, then scattered
clean shells about. Next, they "planted" fertilized oyster eggs, which
within two or three weeks hatched into larvae. The larvae drifted until
they attached themselves to the clean shells on the bottom. There they
remained and in time grew into baby oysters called seed or spat. The spat
grew larger by drawing in seawater from which they derived microscopic
particles of food. Before long, farmers gathered the baby oysters,
transplanted them in other waters to speed up their growth, then
transplanted them once more into another body of water to fatten them up.
Until recently the supply of wild oysters and those crudely farmed were
more than enough to satisfy people's needs.
But today the delectable seafood is no longer available in abundance. The
problem has become so serious that some oyster beds have vanished
entirely.
Fortunately, as far back as the early 1900's marine biologists realized
that if new measures were not taken, oysters would become extinct or
at best a luxury food. So they set up well-equipped hatcheries and
went to work. But they did not have the proper equipment or the skill to
handle the eggs. They did not know when, what, and how to feed the larvae.
And they knew little about the predators that attack and eat baby oysters
by the millions. They failed, but they doggedly kept at it. Finally, in the
1940's a significant breakthrough was made.
The marine biologists discovered that by raising the temperature of the
water, they could induce oysters to spawn not only in the summer but also
in the fall, winter, and spring. Later they developed a technique for
feeding the larvae and rearing them to spat. Going still further, they
succeeded in breeding new strains that were resistant to diseases, grew
faster and larger, and flourished in water of different salinities and
temperatures. In addition, the cultivated oysters tasted better! 
過去人們飼養牡蠣的方式很大程度上類似于田地里的農夫種植蕃茄--通過移植來飼養 它們。
首先，農夫選好牡蠣苗床，清除底部的舊殼和其它雜物，然后四處撒播干凈的殼。 接 著，他們"栽種"已受精的牡蠣卵。 這些卵在 2～3 周內會孵化成幼貝。 幼貝一直漂流直到 粘在苗床底部干凈的殼上為止。 它們會呆在那兒并逐漸長成小牡蠣。 我們稱之為種子或貝苗。 貝苗吸進海水中的微小生物作為食物從而越長越大。 不久之后，農夫將這些小牡蠣收集起來，把它們移種進其他的水域加快其生長，然后再次將它們移種進另外的水域以使其肥 壯起來。 直到最近，野生的以及人工飼養的牡蠣完全能夠滿足人們的需要。但是今天這種可口的海味已不再大量存在。這個問題已經變得如此嚴重以至于一些牡蠣苗床已完全消失。 幸運的是，早在 20 世紀初期海洋生物學家們就意識到如果不采取新的措施，牡蠣將會滅絕 或至少會變為一種奢侈的食品。 因此他們建造了裝備良好的孵卵場所并開始工作。 但是他們尚沒有適當的裝置或技術來處理牡蠣卵。他們不知道何時、用什么以及如何喂養幼貝。他 們對捕食數百萬幼小牡蠣的動物天敵也所知無幾。他們失敗了，但他們頑強地堅持了下來。 終于，在 20 世紀 40 年代，一個重要的突破性的進展產生了。 海洋生物學家發現，升高水溫能夠誘導牡蠣不僅在夏季也在秋季、冬季和春季里產卵。 后來他們發展了一項技術來喂 養幼貝至其長成貝苗。他們進一步成功地培養出了新的品種，可以抵抗疾病、長得更快、 更大并且在不同的鹽度和溫度的水中都能茁壯生長。此外，這些培殖出的牡蠣口感更佳!
35） Oil Refining（煉油） An important new industry, oil refining, grew after the Civil War. Crude
oil, or petroleum -- a dark, thick ooze from the earth -- had been known
for hundreds of years, but little use had ever been made of it. In the
1850's Samuel M. Kier, a manufacturer in western Pennsylvania, began
collecting the oil from local seepages and refining it into kerosene.
Refining, like smelting, is a process of removing impurities from a raw
material.
Kerosene was used to light lamps. It was a cheap substitute for
whale oil, which was becoming harder to get. Soon there was a large
demand for kerosene. People began to search for new supplies of petroleum.
The first oil well was drilled by E. L. Drake, a retired railroad
conductor. In 1859 he began drilling in Titusville, Pennsylvania. The whole
venture seemed so impractical and foolish that onlookers called it "Drake's
Folly". But when he had drilled down about 70 feet (21 meters), Drake
struck oil. His well began to yield 20 barrels of crude oil a day.
News of Drake's success brought oil prospectors to the scene. By the early
1860's these wildcatters were drilling for "black gold" all over western
Pennsylvania. The boom rivaled the California gold rush of 1848 in its
excitement and Wild West atmosphere. And it brought far more wealth to
the prospectors than any gold rush.
Crude oil could be refined into many products. For some years kerosene
continued to be the principal one. It was sold in grocery stores and
door-to-door. In the 1880's refiners learned how to make other petroleum
products such as waxes and lubricating oils. Petroleum was not then used to
make gasoline or heating oil. 
一種重要的新興工業--煉油業在國內戰爭后成長起來。 未加工的石油，或原油--一種深 色的地下的稠漿--數百年來一直為大眾所知，但是人們卻很少使用過它。
在十九世紀五十 年代，薩繆爾.科爾，賓西法尼亞西部的一位制造商，開始從當地的溢出物中收集石油
并將它煉成煤油。與冶煉礦石一樣，石油提煉是一個從未加工的原料中除去雜質的過程。煤 油被用來點燈。
它是鯨油的一種便宜的替代品，而鯨油正變得越來越難以獲得。 不久就產 生了對煤油的大量需求。人們開始尋找新的石油供應。 第一口油井為瑞克，一個退休的火車檢票員所鉆得。1859 年他開始在賓西法尼亞的泰特斯維爾鉆井。整個的這項
冒險事業看起來是如此不現實和愚蠢以致旁觀者稱之為"鴨子的蠢行"。 (譯者注：Drake's Folly, drake
在這里意含雙關，即指瑞克的名字，又指該詞的本義即鴨子。 )但當瑞克往下鉆 至 70 英尺(21 米)的時候，他發現了石油。 他的油井從此每天生產20 桶原油。 瑞克成功的 消息將石油勘探者們吸引到現場。 截止到 19 世紀 60 年代早期，這些冒險者為尋找"黑色的金子"鉆探遍了整個賓西法尼亞西部。 這項繁榮的事業在刺激性和粗獷的西部氣氛上可與1848 年的加州淘金熱相媲美，而且它為勘探者帶來了遠超過淘金潮的財富。 原油能被提煉 成許多產品。 多年以來煤油一直是主要的一種產品。它在雜貨店中出售由人挨戶推銷。 19 世紀八十九十年代煉油者們懂得了生產其它石油產品，如蠟和潤滑油。 那時石油還沒有被用來制造汽油或采暖裝置用油。
36) Plate Tectonics and Sea-floor Spreading(板塊結構與海床擴展)The theory of plate tectonics describes the motions of the lithosphere, the
comparatively rigid outer layer of the Earth that includes all the crust
and part of the underlying mantle. The lithosphere is divided into a few
dozen plates of various sizes and shapes, in general the plates are in
motion with respect to one another. A mid-ocean ridge is a boundary
between plates where new lithospheric material is injected from belows. As
the plates diverge from a mid-ocean ridge they slide on a more yielding
layer at the base of the lithosphere.
Since the size of the Earth is essentially constant, new lithosphere can
be created at the mid-ocean ridges only if an equal amount of lithospheric
material is consumed elsewhere. The site of this destruction is another
kind of plate boundary: a subduction zone. There one plate dives under the
edge of another and is reincorporated into the mantle. Both kinds of plate
boundary are associated with fault systems, earthquakes and volcanism, but
the kinds of geologic activity observed at the two boundaries are quite
different. 
The idea of sea-floor spreading actually preceded the theory of plate
tectonics. In its original version, in the early 1960's, it described the
creation and destruction of the ocean floor, but it did not specify rigid
lithospheric plates. The hypothesis was substantiated soon afterward by the
discovery that periodic reversals of the Earth's magnetic field are
recorded in the oceanic crust. As magma rises under the mid-ocean
ridge, ferromagnetic minerals in the magma become magnetized in the
direction of the geomagnetic field. When the magma cools and solidifies,
the direction and the polarity of the field are preserved in the magnetized
volcanic rock. Reversals of the field give rise to a series of magnetic
stripes running parallel to the axis of the rift. The oceanic crust thus
serves as a magnetic tape recording of the history of the geomagnetic field
that can be dated independently; the width of the stripes indicates the
rate of the sea-floor spreading.
板塊結構理論描述巖石圈的運動。 巖石圈是相對堅硬的地球外層，包括全部地殼和部 分地幔。 巖石圈被劃分為幾十個大小不同形狀各異的板塊，一般而言這些板塊都處于相對 運動之中。 一道中海脊是板塊之間的邊界，在那里新的巖石圈的物質從下部注入。 當板塊從中海脊脫離時，它們滑向在巖石圈基部較易變形的地層上。 因為地球的大小本質上是不變的，只有同等數量的巖石圈物質在其它地方被吞沒，新的巖石圈才能生成。銷毀舊巖石
圈的地方形成另外一種板塊邊界：一塊潛沒的區域。 在這里，一塊板塊潛沒到另一板塊的 邊緣之下并結合入地幔之中。
兩種板塊邊界均與地層系統、地震以及火山活動有關，但在 兩種邊界處觀察到的諸般地質活動卻迥然不同。 海床擴展說實際上早于板塊結構理論。在20 世紀 60 年代它的理論雛形中，描述了海底的生成和毀滅，但沒有詳細介紹堅硬的巖石圈 板塊。 這個假定不久之后為發現所證實。該發現表明地球磁場周期性的逆轉被記錄在海洋 地殼中。 當巖漿從中海脊下涌起的時候，巖漿中的磁鐵礦物質按地磁場的方向被磁化。巖漿冷卻并凝固下來后，地磁場的方向和磁極被保留在磁化了的火山巖中。 磁場的逆轉形成 一系列與斷層軸線平行的條形磁區。這樣海洋殼就扮演了磁帶的角色，記錄下可以鑒定時 間的地磁場的歷史。 條形磁區的寬度表明了海底擴展的速度。
37) Icebergs (冰山)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 case 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 or 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，一種朦朧神秘的氣氛 籠罩著它們。 冰山形成于久遠的、寒冷的水體中，而且伴隨著雷聲轟鳴般的嘈雜和水花洶涌的風暴，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里，與它們保持一段安全距離也是明智的。 冰山的 大部分體積穩藏于水下，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 時間后融化。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后積累了巨大的深度。 由于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 終較底層的晶體合并成龐大而堅固的冰塊。
38) Topaz(黃水晶)Topaz is a hard, transparent mineral. It is a compound of aluminum, silica,
and fluorine. Gem topaz is valuable. Jewelers call this variety of the
stone "precious topaz". The best-known precious topaz gems range in color
from rich yellow to light brown or pinkish red. Topaz is one of the hardest
gem minerals. In the mineral table of hardness, it has a rating of 8, which
means that a knife cannot cut it, and that topaz will scratch quartz.
The golden variety of precious topaz is quite uncommon. Most of the world's
topaz is white or blue. The white and blue crystals of topaz are large,
often weighing thousands of carats. For this reason, the value of topaz
does not depend so much on its size as it does with diamonds and many other
precious stones, where the value increases about four times with each
doubling of weight. The value of a topaz is largely determined by its
quality. But color is also important: blue topaz, for instance, is often
irradiated to deepen and improve its color.
Blue topaz is often sold as aquamarine and a variety of brown quartz is
widely sold as topaz. The quartz is much less brilliant and more plentiful
than true topaz. Most of it is a variety of amethyst: that heat has turned
brown. 
黃水晶是一種堅硬、透明的礦物質。 它是鋁、硅和氟的化合物。 黃水晶寶石價值不菲。 珠寶商把這種石頭稱為"黃玉"。
最出名的黃玉有各種顏色如深黃色、淡棕色、淺紅色等。 黃 水晶是最堅硬的寶石礦中的一種。 在礦石硬度表上，它的硬度為 8，這表明刀子不能割開它而它可在石英上劃痕。 金黃色的黃玉品種非常罕見。 世界上大多數的黃水晶是白色或藍 色的。 這些白色或藍色的黃水晶晶體很大，常常有數千克拉重。
由于這個原因，黃水晶的 價值不像鉆石和許多其它寶石那樣主要依賴于其大小，重量翻一番價值即上升約四倍。 黃
水晶的價值很大程度上取決于其品質，但顏色也很重要。 舉例來說，藍色的黃水晶常需放 射處理以加深和改善其顏色。
藍色的黃水晶常被作為海藍寶石出售，許多種棕色石英被當 作黃水晶廣為販賣。 石英光亮度遠小于黃水晶，礦藏儲量也遠較黃水晶豐富。 大多數石英是一種紫水晶，高溫使其變為棕色。
39) The Salinity of Ocean Waters(海水鹽度) If the salinity of ocean waters is analyzed, it is found to vary only
slightly from place to place. Nevertheless, some of these small changes are
important. There are three basic processes that
cause a change in oceanic salinity.
One of these is the subtraction of water from the ocean by means of
evaporation - conversion of liquid water to water vapor. In this manner the
salinity is increased, since the salts stay behind. If this is carried to
the extreme, of course, white crystals of salt would be left behind.
The opposite of evaporation is precipitation, such as rain, by which
water is added to the ocean. Here the ocean is being diluted so that the
salinity is decreased. This may occur in areas of high rainfall or in
coastal regions where rivers flow into the ocean. Thus salinity
may be increased by the subtraction of water by evaporation, or decreased
by the addition of fresh water by precipitation or runoff.
Normally, in tropical regions where the sun is very strong, the ocean
salinity is somewhat higher than it is in other parts of the world where
there is not as much evaporation. Similarly, in coastal regions where
rivers dilute the sea, salinity is somewhat lower than in other oceanic
areas.
A third process by which salinity may be altered is associated with the
formation and melting of sea ice. When sea water is frozen, the dissolved
materials are left behind. In this manner, sea water directly beneath
freshly formed sea ice has a higher salinity than it did before the ice
appeared. Of course, when this ice melts, it will tend to decrease the
salinity of the surrounding water. In the Weddell Sea Antarctica, the
densest water in the oceans is formed as a result of this freezing process,
which increases the salinity of cold water. This heavy water sinks and is
found in the deeper portions of the oceans of the world. 
如果我們分析海水的鹽度，會發現地區間只有輕微的變化，然而有些小的變化是重要的。
導致海洋的鹽度變化的基本過程有三個，其中之一是通過蒸發的方式即把液態水轉化為水蒸 氣來減少海洋中的水分。 這樣由于鹽留了下來，所以鹽度增大。當然，如果這種方式走向 極端，將會余下白色的鹽晶體。 與蒸發相反的是降水，如降雨，由此水被加入海中，海水 被稀釋，從而鹽度降低。這種情形會發生在大量降雨的地區，或江河入海岸處。 因此，鹽 度通過蒸發減少水分而上升或通過降水或徑流增加淡水成分而下降。 一般來說，在陽光很強烈的熱帶地區，海水的鹽度略高于世界上其它沒有熱帶那樣多的蒸發的地區。 同理，在 江河稀釋海水的海岸地帶，海水鹽度略低于其它海區。第三個可以變更鹽度的過程與海洋 中冰的形成和融化有關。 海水凍結時，溶于其中的物質被留了下來。 這樣，在新形成的海水冰面的正下方的海水比在冰形成之前有更高的鹽度。當然，當冰融化的時候，會降低周 圍水中的鹽度。
在南極洲邊緣的威德爾海中，結冰過程增加低溫海水的鹽度，從而形成了 濃度最大的海水。 這些大密度的海水下沉，可以在世界海洋的深水域發現。
40) Cohesion-tension Theory(內聚壓力理論)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. 
大氣壓能夠支持 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干仍能將水輸送到相當可觀的高度。 對于植物中輸送水的其它解釋都基于根壓--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，那么我們會問：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。 一株植物中作用于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。 由于水從葉子表面喪 失，一個負壓力，或張力就得以產生。 蒸發出去的水被植物里流動的水代替。 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持著這些不斷的水柱。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 支水柱的強度相當于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。
41) American Black Bears(美國黑熊) American black bears appear in a variety of colors despite their name. In
the eastern part of their range, most of these bears have shiny black fur,
but in the west they grow brown, red, or even yellow coats. To the north,
the black bear is actually gray or white in color. Even in the same litter,
both brown and black furred bears may be born.
Black bears are the smallest of all American bears, ranging in length from
five to six feet, weighing from three hundred to five hundred pounds. Their
eyes and ears are small and their eyesight and hearing are not as good as
their sense of smell.
Like all bears, the black bear is timid, clumsy, and rarely dangerous, but
if attacked, most can climb trees and cover ground at great speeds. When
angry or frightened, it is a formidable enemy.
Black bears feed on leaves, herbs, roots, fruit, berries, insects, fish,
and even larger animals. One of the most interesting characteristics of
bears, including the black bear, is their winter sleep. Unlike squirrels,
woodchucks, and many other woodland animals, bears do not
actually hibernate. Although the bear does not eat during the winter months,
sustaining itself from body fat, its temperature remains almost normal, and
it breathes regularly four or five times per minute.
Most black bears live alone, except during mating season. They prefer
to live in caves, hollow logs, or dense thickets. A litter of one to four
cubs is born in January or February after a gestation period of six to nine
months, and they remain with their mother until they are fully grown or
about one and a half years old. Black bears can live as long as thirty
years in the wild, and even longer in game preserves set aside for them. 
美國黑熊雖然被叫做黑熊但卻有各種各樣的顏色。 在它們生活區域的東部，大部分黑 熊長有富有光澤的黑毛，但在西部，他們則長著棕色、紅色甚至是黃色的毛。
在北部，黑 熊其實長著灰色或白色的毛。 就是在一胎所生的小熊中，都可能混雜棕毛和黑毛。 黑熊是 所有美洲熊中最小的，5～6 英尺長，300～500 磅重。 它們的眼睛和耳朵都很小，他們的視 力和聽覺不如嗅覺那樣好。 像所有的熊一樣，黑熊膽小，笨拙，很少具有危險性。但如果受到攻擊，大部分黑熊會以很快的速度爬上樹和奔跑。 當發怒或受驚嚇時，黑熊會成為可 怕的對手。
黑熊以樹葉、草、樹根、水果、漿果、昆蟲、魚，甚至更大的動物為食。 熊類， 包括黑熊的最有趣的一個特點是他們的冬眠。
與松鼠、旱獺和其它別的林地動物不同，熊 并不真正地冬眠。 雖然熊在冬天的幾個月中不吃東西，靠體內脂肪維持生命，但它們的體溫保持正常，并有規律地一分鐘呼吸 4 或 5 次。除交配季節外，大多數黑熊獨自生活。 他 們喜歡住在洞里、空心的大木頭里或茂密的樹叢里。 經過 6 到 9 個月的懷孕期后一胎 1～4 個小熊在 1 月或 2 月出生。 它們同母熊住在一起，直到它們完全長大，即 1 歲半左右。黑熊在野外可以活到長達 30 年，在專門的保護區中甚至能活得更長。
42) Coal-fired Power Plants(火力發電廠)The invention of the incandescent light bulb by Thomas A. Edison in 1879
created a demand for a cheap, readily available fuel with which to generate
large amounts of electric power. Coal seemed to fit the bill, and it fueled
the earliest power stations (which were set up at the end of the nineteenth
century by Edison himself). As more power plants were constructed
throughout the country, the reliance on coal increased. Since the First
World War, coal-fired power plants have accounted for about half of the
electricity produced in the United States each year. In 1986 such plants
had a combined generating capacity of 289, 000 megawatts and consumed 83
percent of the nearly 900 million tons of coal mined in the country that
year. Given the uncertainty in the future growth of nuclear power and in
the supply of oil and natural gas, coal-fired power plants could well
provide up to 70 percent of the electric power in the United States by the
end of the century.
Yet, in spite of the fact that coal has long been a source of electricity
and may remain one for many years (coal represents about 80 percent
of United States fossil-fuel reserves), it has actually never been
the most desirable fossil fuel for power plants. Coal contains less energy
per unit of weight than natural gas or oil; it is difficult to transport,
and it is associated with a host of environmental issues, among them acid
rain. Since the late 1960's problems of emission control and waste disposal
have sharply reduced the appeal of coal-fired power plants. The cost of
ameliorating these environmental problems along with the rising cost of
building a facility as large and complex as a coal-fired power plant,
have also made such plants less attractive from a
purely economic perspective.
Changes in the technological base of coal-fired power plants could restore
their attractiveness, however. Whereas some of these changes are
evolutionary and are intended mainly to increase the productivity of
existing plants, completely new technologies for burning coal cleanly are
also being developed.
托馬斯.愛迪生 1879 年發明的白熾燈導致對便宜、易得、可生產大量電能 的燃料的需求。
煤似乎符合這個要求，并成為第一批電廠的燃料(正是愛迪生本人在 19 世 紀末建造了第一批電廠)。 全國到處興建電廠時，對煤的依賴加深了。自第一次世界大戰 以來，美國每年約有一半的電力是以煤為燃料的電廠提供的。 1986 年這些電廠的總發電能 力達到 28，900千瓦并且消耗了當年全國開采的九億噸煤的 83%。 考慮到核能發展以及石 油、天然氣供應中的不確定因素，到本世紀末，火力發電廠仍可能為美國提供多達 70%的 電力。 然而，盡管煤長期以來一直是電力的原料之一并且可能會繼續如此(煤占美國化石燃 料儲量的 80%)，它卻不是電廠的理想燃料。煤的單位能量含量低于石油和天然氣，而且會 導致包括酸雨在內的一系列環境問題。 從 1960 年以來，排放控制和垃圾處理的問題極大地削弱了燃煤電廠的魅力。 由于減輕這些環境問題需要大量資金，而且建造龐大復雜的燃煤 電廠的費用不斷上漲，也使得這些電廠從經濟角度上不具備吸引力。改變火力發電廠的基 礎技術卻可能恢復它們的吸引力。 雖然某些技術改進是漸進的，其目的只是提高現有電廠 的生產率，但人們正在開發全新的清潔燃煤的技術。
43) Statistics(統計學） There were two widely divergent influences on the early development of
statistical methods. Statistics had a mother who was dedicated to keeping
orderly records of governmental units (state and statistics come from the
same Latin root status) and a gentlemanly gambling father who relied on
mathematics to increase his skill at playing the odds in games of chance.
The influence of the mother on the offspring, statistics, is represented
by counting, measuring, describing, tabulating, ordering, and the
taking of censuses -- all of which led to modern descriptive
statistics. From the influence of the father came modern inferential
statistics, which is based squarely on theories of probability.
Descriptive statistics involves tabulating, depicting and describing
collections of data. These data may be quantitative such as measures of
height, intelligence or grade level -- variables that are characterized by
an underlying continuum -- or the data may represent qualitative variables,
such as sex, college major or personality type. Large masses of data must
generally undergo a process of summarization or reduction before they are
comprehensible. Descriptive statistics is a tool for describing or
summarizing or reducing to comprehensible form the properties of an
otherwise unwieldy mass of data.
Inferential statistics is a formalized body of methods for solving another
class of problems that present great difficulties for the unaided
human mind. 
This general class of problems characteristically
involve attempts to make predictions using a sample of
observations. For example, a school superintendent wishes to determine the
proportion of children in a large school system who come to school without
breakfast, have been vaccinated for flu, or whatever. Having a little
knowledge of statistics, the superintendent would know that it is
unnecessary and inefficient to question each child: the proportion for the
entire district could be estimated fairly
accurately from a sample of as few as 100 children. Thus, the purpose of
inferential statistics is to predict or estimate characteristics of a
population from a knowledge of the characteristics of only a sample of the
population.
統計方法的早期發展受到兩種截然不同的影響。 統計學有一個"母親"，她致力于井井有條地記錄政府機構的文件(國家和統計學這兩個詞源于同一個拉丁語詞根，status)，還有一個有紳士般的賭博"父親"，他依靠數學來提高賭技，以便在幾率的游戲中取勝。 "母親"對其子女統計學的影響表現在計數、測量、描述、制表、歸類和人口普查。 所有這些導致了 現代描述統計學的誕生。
由于"父親"的影響則產生了完全基于概率論原理的現代推理統計 學。 描述統計學涉及對所收集數據的制表、制圖和描述。 這些數據可以是數量性的數據，如高度、智商、或者是層級性的數據--具有連續性的變量--或數據也可以代表性質變量，如 性別、大學專業或性格類型等等。數量龐大的數據通常必須經過概括或刪減的程序才能為 人所理解。 描述統計學就是這樣一個工具，它對極其龐雜的數據進行描述、概括或刪減，使其變成能為人理解的東西。 推理統計學是一套已定形了的方法體系，它解決的是光憑人 腦極難解決的另一類問題。這類問題的顯著特點是試圖通過取樣調查來作出預測。 例如， 有一位教育督察想知道在一個龐大的學校系統中，不吃早飯就上學的學生、已經做過防感冒免疫的學生，或其它任何類型的學生占多大比例。 若具備一些統計學的知識，這位督察應 明白，詢問每個孩子是沒有必要而且沒有效率的，只要用 100個孩子為樣本，他就可以相當 精確地得出這些孩子占整個學區的比例了。 因此，推理統計學的目的就是通過了解一個群
體中一些樣本的特性，從而對整個群體的特性進行推測和估算。
44）Obtaining Fresh Water from Icebergs（從冰山中獲取淡水）The concept of obtaining fresh water from icebergs that are towed to
populated areas and arid regions of the world was once treated as a joke
more appropriate to cartoons than real life. But now it is being
considered quite seriously by many nations, especially since scientists
have warned that the human race will outgrow its fresh water supply faster
than it runs out of food.
Glaciers are a possible source of fresh water that has been
overlooked until recently. Three-quarters of the Earth's fresh water
supply is still tied up in glacial ice, a reservoir of untapped fresh
water so immense that it could sustain all the rivers of the world for
1,000 years. Floating on the oceans every year are 7,659 trillion metric
tons of ice encased in 10,000 icebergs that break away from the polar ice
caps, more than ninety percent of them from Antarctica.
Huge glaciers that stretch over the shallow continental shelf give birth to
icebergs throughout the year. Icebergs are not like sea ice, which is
formed when the sea itself freezes, rather, they are formed entirely on
land, breaking off when glaciers spread over the sea. As they drift away
from the polar region, icebergs sometimes move mysteriously in a direction
opposite to the wind, pulled by subsurface currents. Because they melt more
slowly than smaller pieces of ice, icebergs have been known to drift as far
north as 35 degrees south of the equator in the Atlantic Ocean. To corral
them and steer them to parts of the world where they are needed would not
be too difficult.
The difficulty arises in other technical matters, such as the
prevention of rapid melting in warmer climates and the funneling of
fresh water to shore in great volume. But even if the icebergs lost half
of their volume in towing, the water they could provide would be far
cheaper than that produced by desalinization, or removing salt from water. 
把冰山拖到世界上人口稠密的地區和干旱地帶，再從中獲取淡水，這個想法曾一度被認為是一個笑話，更適合于卡通畫，而非現實生活。 然而現在，許多國家正相當認真地考慮 這件事情，特別是在科學家們發出警告之后。
科學家們認為人類將在耗盡糧食之前首先耗 盡淡水資源。冰川是一個直到最近以前一直被忽視的可能的淡水源。 全球四分之三的淡水 還鎖在冰川的冰塊中。冰川就是一個蓄水池，其中未開發的淡水量是如此巨大，足夠支持 全世界的江河 1000 年。 每年有 7，659 萬億公噸冰漂流在海洋中。它們包含在 10，000 座從極地冰帽中斷裂出來的冰山中。 這些冰山的 90%以上來自南極。 一年四季里，覆蓋在淺層大陸架上的巨大冰川生成了眾多冰山。 冰山和海水的冰不同，后者是海水自身結冰 形成的，而冰山則完全是在陸地上形成的。當冰川伸展到海水中時，冰山就斷裂下來。 當 漂離極地地區時，冰山有時會在底層洋流的推動下頗為神秘地逆風移動。 由于冰山比小塊的冰融化要慢，因此有的冰山在大西洋中向北飄到了赤道以南 35°的地方。 把冰山蓄攔起 來并拖到世界上需要它們的地方將不會太困難。有困難的是其它的技術事宜。 比如，如何 防止冰山在較暖的氣候中迅速融化以及如何把大量的淡水收集到岸上去。 但是，即便在拖的過程中冰山失去了一半體積，這樣做也遠比從海水中脫鹽取得淡水便宜。
45） The Source of Energy（能量的來源） A summary of the physical and chemical nature of life must begin, not on
the Earth, but in the Sun; in fact, at the Sun's very center. It is here
that is to be found the source of the energy that the Sun constantly pours
out into space as light and heat. This energy is liberated at the center of
the Sun as billions upon billions of nuclei of hydrogen atoms collide with
each other and fuse together to form nuclei of helium, and in doing so,
release some of the energy that is stored in the nuclei of atoms. The
output of light and heat of the Sun requires that some 600 million tons of
hydrogen be converted into helium in the Sun every second. This the Sun
has been doing for several thousands of millions of years. The nuclear
energy is released at the Sun's center as high-energy gamma radiation, a
form of electromagnetic radiation like light and radio waves, only of very
much shorter wavelength. This gamma radiation is absorbed by atoms inside
the Sun to be reemitted at slightly longer wavelengths. This radiation, in
its turn is absorbed and reemitted. As the energy filters through the
layers of the solar interior, it passes through the X-ray part of the
spectrum eventually becoming light. At this stage, it has reached what we
call the solar surface, and can escape into space without being absorbed
further by solar atoms. A very small fraction of the Sun's light and
heat is emitted in such directions that after passing unhindered
through interplanetary space, it hits the Earth. 
概說生命的物理和化學特性必須始于太陽--確切地說，是太陽的核心，而非地球。 能 量來自太陽的核心。
在這里，太陽不停地以光和熱的形式向空間傾瀉出能量。 數十億計的 氫原子核在太陽的核心碰撞并且聚變生成氦。 在此過程中一部分原本儲存于原子核中的能量被釋放出來。 太陽所產生的光和熱需要每秒將六億噸氫轉化為氦。 這樣的轉化在太陽中已經持續幾十億年了。 核能在太陽的核心被釋放為高能的伽馬射線。 這是一種電磁射線， 就象光波和無線電波一樣，只是波長要短得多。這種伽瑪射線被太陽內的原子所吸收，然 后重新釋放為波長稍長一些的光波。 這新的射線再次被吸收，而后釋放。 在能量由太陽內部一層層滲透出來的過程中，它經過了光譜中 X 射線部分，最后變成了光。 在此階段，能量到達我們所稱的太陽表層，并且離散到空間而不再被太陽原子所吸收。 只有很小一部分 太陽的光和熱由此方向釋放出來，并且未被阻擋，穿越星空，來到地球。
46） Vision（視覺）Human vision like that of other primates has evolved in an arboreal
environment. In the dense complex world of a tropical forest, it is more
important to see well than to develop an acute sense of smell. In the
course of evolution members of the primate line have acquired large eyes
while the snout has shrunk to give the eye an unimpeded view. Of mammals
only humans and some primates enjoy color vision. The red flag is
black to the bull. Horses live in a monochrome world. Light
visible to human eyes however occupies only a very narrow band in the whole
electromagnetic spectrum. Ultraviolet rays are invisible to humans
though ants and honeybees are sensitive to them. Humans have no direct
perception of infrared rays unlike the rattlesnake which has receptors
tuned into wavelengths longer than 0.7 micron. The world would look eerily
different if human eyes were sensitive to infrared radiation. Then instead
of the darkness of night, we would be able to move easily in a strange
shadowless world where objects glowed with varying degrees of intensity.
But human eyes excel in other ways. They are in fact remarkably discerning
in color gradation. The color sensitivity of normal human vision is rarely
surpassed even by sophisticated technical devices. 
人類的視覺，和其它靈長目動物的一樣，是在叢林環境中進化出來的。 在稠密、復雜的熱帶叢林里，好的視覺比靈敏的嗅覺更加重要。在進化過程中，靈長目動物的眼睛變大， 同時鼻子變小以使視野不受阻礙。 在哺乳類動物中，只有人和一些靈長目動物能夠分辨顏色。紅旗在公牛看來是黑色的，馬則生活在一個單色的世界里。 然而，人眼可見的光在整
個光譜中只占一個非常狹窄的頻段。人是看不到紫外線的，盡管螞蟻和蜜蜂可以感覺到。與 響尾蛇不同，人也不能直接感受到紅外線。響尾蛇的感覺器可以感受波長超過 0.7 微米的 光線。 如果人能感受到紅外線的話，這世界看上去將十分不同，而且恐怖。 到那時，將與夜的黑暗相反，我們能輕易地在一個奇異的沒有陰影的世界里走動。 任何物體都強弱不等 地閃著光。 然而，人眼在其它方面有優越之處。事實上，人眼對顏色梯度具有非凡的分辨 能力。 普通人類的視覺感受色彩的靈敏程度，甚至連精密的技術裝備都很難超越。
47） Folk Cultures A folk culture is a small isolated, cohesive, conservative, nearly
self-sufficient group that is homogeneous in custom and race with a strong
family or clan structure and highly developed rituals. Order is maintained
through sanctions based in the religion or family and interpersonal
relationships are strong. Tradition is paramount, and change comes
infrequently and slowly. There is relatively little division of labor into
specialized duties. Rather, each person is expected to perform a great
variety of tasks, though duties may differ between the sexes. Most
goods are handmade and subsistence economy prevails. Individualism is
weakly developed in folk cultures as are social classes. Unaltered folk
cultures no longer exist in industrialized countries such as the United
States and Canada. Perhaps the nearest modern equivalent in Anglo America
is the Amish, a German American farming sect that largely renounces the
products and labor saving devices of the industrial age. In Amish
areas, horse drawn buggies still serve as a local transportation
device and the faithful are not permitted to own automobiles. The Amish's
central religious concept of Demut "humility", clearly reflects the
weakness of individualism and social class so typical of folk cultures and
there is a corresponding strength of Amish group identity. Rarely do the
Amish marry outside their sect.民間文化民間 The religion, a variety of the
Mennonite faith, provides the principal mechanism for maintaining orders.
By contrast a popular culture is a large heterogeneous group often highly
individualistic and constantly changing. Relationships tend to be
impersonal and a pronounced division of labor exists, leading to the
establishment of many specialized professions. Secular institutions of
control such as the police and army take the place of religion and family
in maintaining order, and a money-based economy prevails. Because of these
contrasts, "popular" may be viewed as clearly different from "folk". The
popular is replacing the folk in industrialized countries and in many
developing nations. Folk-made objects give way to their popular equivalent,
usually because the popular item is more quickly or cheaply produced, is
easier or time saving to use or leads more prestige to the owner.
文化是小型的、孤立的、緊密的、保守的、近乎自給自足的群體，具有同 樣的習俗、同樣的人種和強有力的家庭或部族結構以及高度發展的宗教儀式。秩序由宗教 或家庭的約束來維持，成員間的關系非常緊密，傳統至高無上，很少有變動且變動緩慢。 勞 動專業分工相對較少。每個人都要做各類活計，盡管男女兩性分工不同。 絕大多數物品是 手工制造的，經濟一般為自給自足型。 個人主義和社會階層在民間文化群體中的發展十分
薄弱。在象美國和加拿大這樣的工業化國家里，一成不變的民間文化群體已不復存在了。在 當代美洲的英語區，與民間文化最相似的群體也許算是 Amish。 Amish 是美國的德裔農耕 部落，他們基本上拒絕接受工業時代的大多數產品和節省勞力的設施。 在 Amish 地區，輕便馬車仍是當地的交通工具，信徒們不允許擁有汽車。 Amish 宗教中的核心觀念 Demut 即 謙卑典型地反映了在民間文化群中個人主義和階級的不發達。
而與此同時，Amish 對群體 的認同性卻十分強。 Amish 人很少和他們宗派以外的人通婚。 其宗教，作為 Mennonite 信仰的一種，提供了維護秩序的主要機制。 相反，大眾文化是包含不同種族的大群體，通常 高度個性化而且不斷在變化。人際關系冷漠，勞動分工明確，由此產生了許多專門的職業。 世俗的控制機構，比如警察和軍隊，取代了宗教和家庭來維持秩序，而且實行的是貨幣經濟。由于存在著這些差異，"大眾的"與"民間的"可謂大相徑庭。 在工業化國家以及許多發展中 國家里，大眾文化正在取代民間文化。民間制造的物品正讓位于大眾化產品，這通常是因 為大眾化的物品制造起來更快、更便宜，用起來更容易、更方便或者是能給其所有者帶來更 多的威望。
48） Bacteria（細菌）Bacteria are extremely small living things. While we measure our own
sizes in inches or centimeters, bacterial size is measured in microns. One
micron is a thousandth of a millimeter: a pinhead is about a millimeter
across. Rod-shaped bacteria are usually from two to four microns long,
while rounded ones are generally one micron in diameter. Thus if you
enlarged a rounded bacterium a thousand times, it would be just about the
size of a pinhead. An adult human magnified by the same amount would be
over a mile (1.6 kilometers) tall.
Even with an ordinary microscope, you must look closely to see
bacteria. Using a magnification of 100 times, one finds that bacteria are
barely visible as tiny rods or dots. One cannot make out anything of their
structure. Using special stains, one can see that some bacteria have
attached to them wavy-looking "hairs" called flagella. Others have only one
flagellum. The flagella rotate, pushing the bacteria through the water.
Many bacteria lack flagella and cannot move about by their own
power, while others can glide along over surfaces by some
little-understood mechanism.
From the bacterial point of view, the world is a very different place from
what it is to humans. To a bacterium water is as thick as molasses is to
us. Bacteria are so small that they are influenced by the movements of
the chemical molecules around them. Bacteria under the microscope,
even those with no flagella, often bounce about in the water. This is
because they collide with the water molecules and are pushed this way and
that. Molecules move so rapidly that within a tenth of a second the
molecules around a bacterium have all been replaced by new ones; even
bacteria without flagella are thus constantly exposed to a changing
environment.
細菌是極其微小的生物體。 我們用英寸或厘米來測量自己的大小，而測量細菌卻 要用微米。 一微米等于千分之一毫米。 針頭直徑大約一毫米。棒狀細菌通常有 2～4 微米 長，而圓形細菌的直徑一般只有 1 微米。 因此，即使你把一個圓形細菌放大 1000 倍，它也 不過一個針頭那么大。可是如果把一個成年人放大 1000 倍，就會變成 1 英里(或 1.6 公里) 多高。 用一般的顯微鏡觀察細菌時，你必須仔細觀察才能看見它們。 使用100 倍的顯微鏡 時，你會發現細菌不過是隱約可見的小細棒或小點點，而它們的結構你卻根本看不出來。 使 用特殊的著色劑后，你會發現有的細菌上長著不少波狀的"毛發"即鞭毛，而有的細菌只有一 根鞭毛。 鞭毛的旋轉可以推動細菌在水中行進。
不少細菌沒有鞭毛，因而不能自己行進。 還有些細菌卻能通過某些鮮為人知的機制沿物體表面滑動。 我們所熟知的世界在細菌眼中 完全是另一個樣子。對于細菌來說，水就同糖漿之于人類一樣稠密。 細菌是如此的微小， 周圍化學分子的一舉一動都會對它們產生影響。 在顯微鏡下，細菌，甚至包括那些沒有鞭毛的細菌，經常在水中跳來跳去。 這是因為它們與水分子相撞后，被彈向各個方向。 分子 移動很迅速，僅 0.1秒之隔，一個細菌周圍的分子就會完全更新。 因此，即使是沒有鞭毛 的細菌也暴露在一個不斷變化的環境中。
49） Sleep （睡眠）Sleep is part of a person's daily activity cycle. There are several
different stages of sleep, and they too occur in cycles. If you are an
average sleeper, your sleep cycle is as follows. When you
first drift off into slumber, your eyes will roll about a bit, your
temperature will drop slightly, your muscles will relax, and your
breathing well slow and become quite regular. Your brain waves slow down a
bit too, with the alpha rhythm of rather fast waves predominating for the
first few minutes. This is called stage 1 sleep. For the next half hour or
so, as you relax more and more, you will drift down through stage 2 and
stage 3 sleep. The lower your stage of sleep, the slower your brain waves
will be. Then about 40 to 60 minutes after you lose consciousness you will
have reached the deepest sleep of all. Your brain waves will show the large
slow waves that are known as the delta rhythm. This is stage 4 sleep.
You do not remain at this deep fourth stage all night long, but instead
about 80 minutes after you fall into slumber, your brain activity level
will increase again slightly. The delta rhythm will disappear, to be
replaced by the activity pattern of brain waves. Your eyes will begin to
dart around under your closed eyelids as if you were looking at something
occurring in front of you. This period of rapid eye movement lasts for some
8 to 15 minutes and is called REM sleep. It is during REM sleep period,
your body will soon relax again, your breathing will grow slow and regular
once more, and you will slip gently back from stage 1 to stage 4 sleep -
only to rise once again to the surface of near consciousness some 80
minutes later.
睡眠是人每天日常活動循環的一部分。 人的睡眠分幾個階段，而這些階段也是循環發 生的。 如果你是一個正常的睡眠者，你的睡眠循環會這樣進行。在你開始昏昏入睡時，你 的眼睛會滾動幾下，體溫略有下降，肌肉放松，呼吸變得緩慢而有節奏。 除了開始幾分鐘 比較快的α節奏外，腦電波也稍有減緩。這被稱為第一階段睡眠。 在隨后約半小時內，你 進一步放松，進入第二和第三階段睡眠。 睡眠越深入，腦電波就越緩慢。 大約在開始睡眠 后的 40 到 60 分鐘，你將進入沉睡狀態。 這時的腦電波表現為巨大的緩波，被稱為δ節奏。 這就是第四階段睡眠。 但你并不是整夜都保持這種沉睡狀態。 入睡后約
80 分鐘左右，你 的大腦運動水平會再度略有提高。 δ節奏消失，并被腦電波的運動圖形取代。你的眼睛會
在閉著的眼瞼下迅速轉動，就好象你在看著眼前發生的什么事情。 這種迅速的眼球運動持 續約 8～15 分鐘，這一階段睡眠被稱之為快速眼動(REM)睡眠。在 REM 睡眠階段，你的肢 體會很快再度放松，呼吸也再次放慢并變得有節奏，你會輕松地從第一階段滑入第四階段睡 眠-直到大約 80分鐘后重新接近清醒狀態。
50） Cells and Temperature （細胞與溫度）Cells cannot remain alive outside certain limits of temperature, and much
narrower limits mark the boundaries of effective functioning. Enzyme
systems of mammals and birds are most efficient only within a narrow range
around 37 ℃; a departure of a few degrees from this value seriously
impairs their functioning. Even though cells can survive wider
fluctuations, the integrated actions of bodily systems are impaired.
Other animals have a wider tolerance for changes of bodily temperature. For
centuries it has been recognized that mammals and birds differ from other
animals in the way they regulate body temperature. Ways of
characterizing the difference have become more accurate and meaningful
over time, but popular terminology still reflects the old division into
"warm blooded" and "cold blooded" species; warm-blooded included
mammals and birds whereas all other creatures were considered cold-blooded.
As more species were studied, it became evident that this classification
was inadequate. A fence lizard or a
desert iguana -- each cold-blooded -- usually has a body temperature only a
degree or two below that of humans and so is not cold. Therefore the next
distinction was made between animals that maintain a constant body
temperature, called homeotherms, and those whose body temperature varies
with their environment, called poikilotherms. But this classification also
proved inadequate, because among mammals there are many that vary their
body temperatures during hibernation. Furthermore, many invertebrates that
live in the depths of the ocean never experience a change in the chill of
the deep water, and their body temperatures remain constant. 
細胞只能在一定的溫度范圍內存活，而進一步保證它們有效工作的溫度范圍就更小了。哺乳動物和鳥類的酶系統只能在 37℃左右的很小范圍內才能有效工作。 與此相差僅幾度的 溫度都會大大削弱它們的工作效率。盡管溫度變化更大時細胞仍能存活，但機體系統的整體運行能力卻被削弱了。 其它動物對體溫的變化有更強的適應性。 幾個世紀以來，人們就 認識到哺乳動物和鳥類調節體溫的方式與其它動物不同。 隨著時間的推移，人們對這種差異的描述越來越精確和有意義，但是"暖血動物"和"冷血動物"這一古老的分類方式至今仍在 大眾詞匯中有所反映。暖血動物包括哺乳動物和鳥類，其它動物統統被視為冷血動物。但是對更多物種進行的研究表明這種分類顯然是不適當的。美洲一種小型蜥蜴和沙漠鬣蜥同
屬冷血動物，但實際上它們的體溫通常只比人類的體溫低 1～2 度，因此并不是真正的冷血。因此又出現了恒溫動物(即保持恒定體溫的動物)和變溫動物(即體溫隨外界環境的變化而改 變的動物)這一區分方式。 但這種分類也不恰當。
因為有不少哺乳動物在冬眠期間會改變 體溫，而許多生活在深海的無脊椎動物在寒冷的深海水域中體溫并不變化，而是恒定的。

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