1. The same thing happens to this day, though on a smaller scale, wherever a sediment-laden river or stream emerges from a mountain valley onto relatively flat land, dropping its load as the current slows: the water usually spreads out fanwise, depositing the sediment in the form of a smooth, fan-shaped slope.
类似事件如今也时常发生，不过规模相对较小罢了。 当携带沉积物的河流或溪水从山谷而下，流至相对平坦的地面时，砂石便随着流速减慢而逐渐沉淀：水流通常呈扇形蔓延，进而使所承载的砂石以光滑扇形的斜面形式沉积下来。
2. If they are now below the water’s upper surface (the water table), the gravels and sands of the former riverbed, and its sandbars, will be saturated with groundwater.
如果这些河床如今正位于地下水位之下，那么其所含的沙石定会储存了大量地下水。
3. But note that porosity is not the same as permeability, which measures the ease with which water can flow through a material; this depends on the sizes of the individual cavities and the crevices linking them.
但注意，多孔性与渗透性是不同概念。渗透性衡量的是水渗透物质的难易程度，它取决于物质中独立孔洞以及连接孔洞的裂缝的大小。
4. If the pores are large, the water in them will exist as drops too heavy for surface tension to hold, and it will drain away; but if the pores are small enough, the water in them will exist as thin films, too light to overcome the force of surface tension holding them in place; then the water will be firmly held.
如果毛孔很大，毛孔中的水会形成过重的水滴，进而可以克服表面张力，从而掉落。
5. But the myths that have grown up around the rites may continue as part of the group conditions divorced from these rites.
但围绕着仪式所产生的神话很可能继续作为该群体口头讲述传统的一部分，并与原有仪式相脱节。
6. Another, advanced in the twentieth century, suggests that humans have a gift for fantasy, through which they seek to reshape reality into more satisfying forms than those encountered in daily life.
另一在12世纪得到发展的理论认为人类具有幻想的天赋，通过幻想人类试图重塑现实，使其变得比现实生活中所遇到的更加令人满意。
7. For example, one sign of this condition is the appearance of the comic vision, since comedy requires sufficient detachment to view some deviations from social norms as ridiculous rather than as serious threats to the welfare of the entire group.
例如，这种情况的一个标志是喜剧观点的出现，因为喜剧要求人们充分地从痛苦中脱离，并将一些与社会准则相偏离的表现看做滑稽可笑的而不是视其为对群体利益的巨大威胁。
8. Timberline trees are normally evergreens, suggesting that these have some advantage over deciduous trees (those that lose their leaves) in the extreme environments of the upper timberline.
树带界线内的树木通常是长青植物，这或许是因为它们与落叶树木相比更适合生存在极其恶劣的环境中。
9. This is particularly true for trees in the middle and upper latitudes, which tend to attain greater heights on ridges, whereas in the tropics the trees reach their greater heights in the valleys.
上行树带界线内的树木通常会扭曲变形，特别是中高纬度地区，那里的树木往往在山脊处长得更高，而热带地区的树木则在山谷里长得更高。
10. As the snow is deeper and lasts longer in the valleys, trees tend to attain greater heights on the ridges, even though they are more exposed to high-velocity winds and poor, thin soils there.
由于山谷中积雪埋藏较深并持续时间很长，树木往往在山脊上长得更高，即便在那里它们要承受更高速的风和更贫瘠的土地。
11. Wind velocity also increases with altitude and may cause serious stress for trees, as is made evident by the deformed shapes at high altitudes.
另外，风速会随着海拔的升高而增加，这很可能给树木施加巨大压力，高海拔树木的变形已很明确地证实了这一点。
12. Some scientists have proposed that the presence of increasing levels of ultraviolet light with elevation may play a role, while browsing and grazing animals like the ibex may be another contributing factor.
一些科学家还提出，随着海拔的上升，紫外线强度也会不断增加，而野生山羊等动物的放养也可能对植物生长产生不利影响。
13. Probably the most important environmental factor is temperature, for if the growing season is too short and temperatures are too low, tree shoots and buds cannot mature sufficiently to survive the winter months.
或许最重要的环境因素是气温，因为如果生长季节过短且气温过低，树芽和花蕊都无法发育成熟，因而无法在冬季存活。
14. Immediately adjacent to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs, herbs, and grasses, while higher up the number and diversity of species decrease until there is much bare ground with occasional mosses and lichens and some prostrate cushion plants.
该区域紧挨林木线，被低矮灌木，草本植物和草地完全覆盖。随着海拔继续升高，物种数量和多样性逐渐降低，直到转变为裸露空地，偶尔伴有苔藓、地衣和倒伏植物的生长。
15. In order for the structure to achieve the size and strength necessary to meet its purpose, architecture employs methods of support that, because they are based on physical laws, have changed little since people first discovered them-even while building materials have changed dramatically.
建筑结构必须达到大小和强度的要求，以实现必要的建筑目的，因此建筑学上采用一些支撑的方法，这些方法都是以物理定律为基础的，尽管建筑材料已经发生了翻天覆地的变化，这些支撑的方法却自人们发现它们以来就鲜有变化。
16. It works in compression to divert the weight above it out to the sides, where the weight is borne by the vertical elements on either side of the arch.
它使得其上的压力转移到两侧，由两侧垂直的部分来承担压力。
17.The fungi absorb moisture and mineral salts from the rocks, passing these on in waste products that nourish algae.
真菌从岩石中吸收水分和矿物盐，并把这些东西传到排泄物用以滋养海藻。
18. The Ogallala aquifer is a sandstone formation that underlies some 583,000 square kilometers of land extending from northwestern Texas to southern South Dakota.
奥加拉拉蓄水层属于砂岩结构，在从德克萨斯州西北到南达科塔州的地下绵延了583000平方公里。
19. Unfortunately, the cost of water obtained through any of these schemes would increase pumping costs at least tenfold, making the cost of irrigated agricultural products from the region uncompetitive on the national and international markets.
不幸的是，通过以上任何一种方式获得水资源都会将抽水的成本提高十倍以上，进而导致这一地区的灌溉农产品成本在国内和国际市场上都毫无竞争力。
20. Whatever the final answer to the water crisis may be, it is evident that within the High Plains, irrigation water will never again be the abundant, inexpensive resource it was during the agricultural boom years of the mid-twentieth century.
无论这次水资源危机的最终结果如何，显然，北美大平原地区灌溉水资源再也不会像20世纪中期农业繁荣时期的那样充足并且廉价了。
21. To take an extreme example, farmlands dominated by a single crop are so unstable that one year of bad weather or the invasion of a single pest can destroy the entire crop.
举个极端的例子，在单一作物的农田中，一年的恶劣天气或单一害虫的入侵就可以摧毁所有作物。
22. Ecologists are especially interested to know what factors contribute to the resilience of communities because climax communities all over the world are being severely damaged or destroyed by human activities.
生态学家们更想弄清楚到底哪些因素有助于促成群落的恢复，因为世界各地的顶极群落都因为人类活动而遭受到严重的损坏或毁坏。
23. The destruction caused by the volcanic explosion of Mount St. Helens, in the northwestern United States, for example, pales in comparison to the destruction caused by humans.
就像美国西北部圣海伦火山的猛烈喷发所造成的破坏，在人类活动对环境造成的的破坏面前也相形见绌。
24. Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the patchiness environment, an environment that varies from place to place supports more kinds of organisms than an environment that is uniform.
现在的很多生态学家们认为，顶极群落相对长期的稳定性并非来于自多样性，而是来自环境的“补缀”，随处变化的环境比统一的环境更有利于多种有机体的生存。
25. Similarly, a plant or animal cannot squander all its energy on growing a big body if none would be left over for reproduction, for this is the surest way to extinction.
类似地，一种植物或者动物不能把所有的能量都用于生长巨大的身躯上如果没有能量用于繁殖，那么必然走向灭亡。
26. At the other extreme are competitors, almost all of whose resources are invested in building a huge body, with a bare minimum allocated to reproduction.
另一个极端方面是竞争对手，几乎所有的资源都被用于建设一个庞大的机构，同时用最低限度（的能量）进行繁殖。
27. A new plant will spring up wherever a seed falls on a suitable soil surface, but because they do not build big bodies, they cannot compete with other plants for space, water, or sunlight.
只要种子落在合适的地面上新植物就会生长出来。
28. These plants are termed opportunists because they rely on their seeds, falling into settings where competing plants have been removed by natural processes, such as along an eroding riverbank, on landslips, or where a tree falls and creates a gap in the forest canopy.
这些植物被称为机会主义者，因为他们依靠自己的种子，种子落入到竞争植物已被自然流程移除的环境中，比如被侵蚀了的河岸，滑坡，或在树倒后在森林冠层形成的一个沟壑里。
29. Human landscapes of lawns, fields, or flowerbeds provide settings with bare soil and a lack of competitors that are perfect habitats for colonization by opportunists.
草坪，田野，花圃这些人文景观提供了赤裸的土壤和缺乏竞争对手的环境，这些环境是机会主义者用来殖民的完美栖息地。
30. A massive oak claims its ground for 200 years or more, outcompeting all other would-be canopy trees by casting a dense shade and drawing up any free water in the soil.
一颗巨大的橡树占据它的领地长达200年甚至更久，通过制造浓密的树荫和吸收土壤中任何多余水分驱逐所有可能的冠层树木。
31. It should be noted, however, that the pure opportunist or pure competitor is rare in nature, as most species fall between the extremes of a continuum, exhibiting a blend of some opportunistic and some competitive characteristics.
然而，值得关注的是，单纯机会主义者或竞争者在自然界中是很少见的，大多数的物种都属于这两个极端组成的区域中，同时具有二者的一些特点。
32. Because some paintings were made directly over others, obliterating them, it is probable that a painting's value ended with the migration it pictured.
由于穴居人通常住在靠近洞口的地方，一定存在某些原因使得世代的拉斯科岩洞穴居者隐藏着他们的艺术作品。
33. One Lascaux narrative picture, which shows a man with a birdlike head and a wounded animal, would seem to lend credence to this third opinion, but there is still much that remains unexplained.
一幅拉斯科岩洞画描绘了一个鸟头人和一个受伤动物的故事，这幅画看起来会增加了这种观点的可信度，但仍有很多疑惑尚未揭开。
34. Perhaps so much time has passed that there will never be satisfactory answers to the cave images, but their mystique only adds to their importance.
或许时间太久，对这些岩洞画解释也可能永远都没有令人满意的答案，但是它们的神秘感会使它们更加重要。
35. In 1994 there were nearly 20,000 wind turbines worldwide, most grouped in clusters called wind farms that collectively produced 3,000 megawatts of electricity.
1994年，世界各地有近2万台风力涡轮机，大量风力涡轮机集中在一起组成风力发电厂，可共同发电3000兆瓦。
36. Most were in Denmark which got 3 percent of its electricity from wind turbines and California where 17,000 machines produced 1 percent of the state s electricity, enough to meet the residential needs of a city as large as San Francisco.
丹麦全国电力的3%来源于风力发电，美国加州风力发电厂17000台涡轮机的发电量占全州电量的1%，足以满足旧金山这种大城市的居住用电需求。
37. In the long run, electricity from large wind farms in remote areas might be used to make hydrogen gas from water during periods when there is less than peak demand for electricity.
长期而言，偏远地区的大型风力发电厂发电量高于用电高峰需求量时，多出的电量可能会为从水中制造氢气提供支持。
38. Large wind farms might also interfere with the flight patterns of migratory birds in certain areas, and they have killed large birds of prey (especially hawks, falcons, and eagles) that prefer to hunt along the same ridge lines that are ideal for wind turbines.
某些区域的大型风力发电厂很可能会影响候鸟的飞行方式，他们杀害了大型猛禽（尤其是老鹰、猎鹰和鹰），这些猛禽喜欢沿那些风力涡轮机所处的嵴线捕食。
39. David Douglas, Scottish botanical explorer of the 1830s， found a disturbing change in the animal life around the fort during the period between his first visit in 1825 and his final contact with the fort in 1832.
十九世纪三十年代，苏格兰植物学探险家大卫·道格拉斯发现了他在1825年第一次的探访和1832年的最后接触之间出现在温哥华堡附近令人不安的变化。
40. The researchers Peter Ucko and Andree Rosenfeld identified three principal locations of paintings in the caves of western Europe: (1) in obviously inhabited rock shelters and cave entrances; (2) in galleries immediately off the inhabited areas of caves; and (3) in the inner reaches of caves, whose difficulty of access has been interpreted by some as a sign that magical-religious activities were performed there.
研究人员彼特·阿寇 和安德烈·罗森菲尔德指出西欧洞画的三个主要地点：（1）在明显有遮蔽可供人类居住的岩石和洞穴入口处，（2）在居住的洞穴一出门的走廊上，（3）在洞穴所能及的最深处，有人认为之所以在最深处作画是因为当时的人们曾在这里进行神秘的宗教活动。
41. Perhaps, like many contemporary peoples, Upper Paleolithic men and women believed that the drawing of a human image could cause death or injury, and if that were indeed their belief, it might explain why human figures are rarely depicted in cave art.
或许，同许多当代人一样，后石器时代的人们也相信画人物像会引起伤害或死亡。如果这确实是他们的信念，那就解释了为什么在洞穴绘画中很少描绘人物。
42. For example, wild cattle (bovines) and horses are portrayed more often than we would expect by chance, probably because they were larger and heavier (meatier) than other animals in the environment.
比如，野牛（牛）和马的出现比我们预料的更为频繁，可能因为它们比其它动物更大更沉（肉更多）。
43. Consistent with this idea, according to the investigators, is the fact that the art of the cultural period that followed the Upper Paleolithic also seems to reflect how people got their food.
看起来接下来的后旧石器时代文化期的艺术也反映了人们如何得到食物，根据调查者的研究，这一事实也与前文的想法一致。
44. But in that period, when getting food no longer depended on hunting large game animals (because they were becoming extinct), the art ceased to focus on portrayals of animals.
但在那个时期，当不再依附于猎取大型猎物获得食物时（因为它们开始变得稀少），岩洞艺术便不再以描绘动物为主了。
45. When the well reaches a pool, oil usually rises up the well because of its density difference with water beneath it or because of the pressure of expanding gas trapped above it.
当井探至油床时，石油通常会上升至井内，因为石油的密度与在下层的水不同，或者因为石油上面的气体扩张形成的压力。
46. More than one-quarter of the world’s oil and almost one-fifth of the world’s natural gas come from offshore, even though offshore drilling is six to seven times more expensive than drilling on land.
世界上四分之一以上的石油和近五分之一的天然气都来自近海，尽管近海钻井的成本比陆地钻井高6至7倍。
47. While there are a dozen or more mass extinctions in the geological record, the Cretaceous mass extinction has always intrigued paleontologists because it marks the end of the age of the dinosaurs.
根据地质史料记载，地球上有十几次甚至更多大型的物种灭绝，古生物学家一直对白垩纪大灭绝非常感兴趣，因为它标志着恐龙时代的结束。
48. The explosion lifted about 100 trillion tons of dust into the atmosphere, as can be determined by measuring the thickness of the sediment layer formed when this dust settled to the surface.
那场爆炸将大量尘埃扬起至大气层中，通过测量沉积岩的厚度，我们可以判断当时的大气中的尘埃约有100万亿吨。
49. Such a quantity of material would have blocked the sunlight completely from reaching the surface, plunging Earth into a period of cold and darkness that lasted at least several months.
如此大量的物质存在于大气层中，将会完全阻隔阳光的照射，于是地球一瞬间进入了一个持续数月之久的寒冷黑暗时期。
50. The explosion is also calculated to have produced vast quantities of nitric acid and melted rock that sprayed out over much of Earth, starting widespread fires that must have consumed most terrestrial forests and grassland.
据估计，爆炸过程还产生了大量的硝酸和被溶解的岩浆并喷出地球外，造成了大面积火灾，大部分的森林和草原被燃尽。
51. Following each mass extinction, there is a sudden evolutionary burst as new species develop to fill the ecological niches opened by the event.
每一次大灭绝过后，都会有新的物种爆炸式地进化去填补由灭绝造成的物种空缺。
52. Earth is a target in a cosmic shooting gallery, subject to random violent events that were unsuspected a few decades ago.
几十年前，地球是宇宙射击场的一个靶子，容易受到未知的随机暴力事件的攻击
53. Early in the century, a pump had come into use in which expanding steam raised a piston in a cylinder，and atmospheric pressure brought it down again when the steam condensed inside the cylinder to form a vacuum．
在（十八）世纪早期，泵曾被用于在气缸中使蒸汽推动活塞，气缸内部的蒸汽被压缩形成真空环境，大气压又使得活塞下降。
54. The final step came when steam was introduced into the cylinder to drive the piston backward as well as forward thereby increasing the speed of the engine and cutting its fuel consumption.
最终，蒸汽被运用于汽缸中将活塞推回，从而加快了机器的运转速度并降低了能源消耗。
55. Iron manufacturers which had starved for fuel while depending on charcoal also benefited from ever-increasing supplies of coal; blast furnaces with steam-powered bellows turned out more iron and steel for the new machinery.
依赖于木炭供应的铁匠们亟需燃料，他们也受益于越来越多的煤炭供应。配备有蒸汽动力的鼓风炉使得越来越多的钢铁供应成为可能。
56. He received rudimentary village schooling but mostly he roamed his uncle's farm collecting the fossils that were so abundant in the rocks of the Cotswold hills．
史密斯只在村里的学校接受了最基本的教育，大部分的时间都是在他叔叔的农场里搜寻化石，这些化石在科茨沃尔德山的岩石里是很常见的。
57. The companies building the canals to transport coal needed surveyors to help them find the coal deposits worth mining as well as to determine the best courses for the canals.
他工作的那家公司致力于开掘一条运河来运输煤矿，需要测量员帮助他们探寻值得挖掘的煤矿所在地，并为他们决定最佳的运河路线。
58. In 1831 when Smith was finally recognized by the Geological Society of London as the “father of English geology”, it was not only for his maps but also for something even more important．
到了1831年，史密斯最终被伦敦地质学会认可，并赋予他“英国地质学之父”的称号，这不仅仅是因为那张地图，而且是为了其他更重要的原因。
59. Maturation of the frontal lobes of the brain continues throughout early childhood, and this part of the brain may be critical for remembering particular episodes in ways that can be retrieved later.
孩子们早期的童年时代中，脑前叶不断地成熟，它对记忆发生的特殊事件以及之后对这些事情的回想起着至关重要的作用。
60. Demonstrations of infants and toddlers' long-term memory have involved their repeating motor activities that they had seen or done earlier，such as reaching in the dark for objects, putting a bottle in a doll apart two pieces of a toy.
婴幼儿长期记忆的形成，还会涉及到他们之前早期看到的或者自身经历的活动的重复，比如：到黑暗的环境里取东西，把瓶子塞到了洋娃娃的嘴里，或者将玩具撕成两半等。
61.Through hearing stories with a clear beginning，middle, and ending children may learn to extract the gist of events in ways that they will be able to describe many years later.
听故事的时候有个清晰的开头、情节和结尾会帮助孩子们提取事件的要点，并且使他们在过了很多年以后仍然可以描述这些事情。
62. The world looks very different to a person whose head is only two or three feet above the ground than to one whose head is five or six feet above it, older children and adults often try to retrieve the names of things they saw, but infants would not have encoded the information verbally．
对于一个头离地面两三尺的孩子来说，这个世界与那些稍大点的孩子眼中的世界不尽相同。长大后的孩子和成人经常试图回忆那些他们曾经见过的事物的名字，但在他们的幼儿时期时尚未对此进行语言化的信息储存。
63.General knowledge of categories of events such as a birthday party or a visit to the doctor's office helps older individuals encode their experiences, but again, infants and toddlers are unlikely to encode many experiences within such knowledge structures．
人们对类似生日聚会或者拜访医生诊所类似事件的分类常识有助于人们记忆他们的经历，但是，婴幼儿时期的孩子们似乎缺乏这些知识结构来帮助他们储存信息。
64.Physiological immaturity may be part of why infants and toddlers do not form extremely enduring memories, even when they hear stories that promote such remembering in preschoolers.
学龄前孩子听到那些可以促进他们回忆的故事时，生理上的不成熟是导致他们无法形成长久记忆的原因之一。
65.In 1947 Norwegian adventurer Thor Heyerdahl drifted on a balsa-log raft westward with the winds and currents across the Pacific from South America to prove his theory that Pacific islanders were Native Americans (also called American Indians).
1947年挪威探险家Thor Heyerdahl为了证明他太平洋居民是美国本土居民（也被称作美国印第安人）的理论，用一只带有标志的轻质木筏，借助风力和水流从南美洲漂流过了太平洋。
66.Contrary to the arguments of some that much of the pacific was settled by Polynesians accidentally marooned after being lost and adrift, it seems reasonable that this feat was accomplished by deliberate colonization expeditions that set out fully stocked with food and domesticated plants and animals.
与那个太平洋人很多都是玻利尼西亚人偶然迷失和漂流而定居下来的说法相反的是，这些功绩是通过有意的殖民远征来实现的，他们那些准备周详的，出发时满载食物、已驯化的植物和动物。
67. “The undisputed pre-Columbian presence in Oceania of the sweet potato, which is a New World domesticate, has sometimes been used to support Heyerdahl’s “American Indians in the Pacific” theories.
土豆，一种新世界的品种，哥伦比亚发现美洲大陆前它就在大洋洲的出现是无可置疑的，这有时候被用来证明Heyerdahl的美国印第安人在太平洋的理论。
68.As Patrick Kirch, an American anthropologist, points out, rather than being brought by rafting South Americans, sweet potatoes might just have easily been brought back by returning Polynesian navigators who could have reached the west coast of South America.
正如美国人类学家Patrick Kirch所指出的，比起从南美漂流过来，土豆更容易被那些到过南美的玻利尼西亚返航者携带来。
69.Conditions that promote fossilization of soft-bodied animals include very rapid covering by sediments that create an environment that discourages decomposition.
促使软体动物成为化石的条件是沉积物的迅速覆盖以形成一个抑制分解的环境。
70.This 700-million-year-old formation gives few clues to the origins of modern animals, however, because paleontologists believe it represents an evolutionary experiment that failed.
这些7亿年前形成的地层为现代动物的起源提供了一些新的线索，但是由于古生物学家们认为它代表着一次失败的进化试验。
71.At one time, the animals present in these fossil beds were assigned to various modern animal groups, but most paleontologists now agree that all Tommotian fossils represent unique body forms that arose in the early Cambrian period and disappeared before the end of the period, leaving no descendants in modern animal groups.
在一段时间内，人们认为这些化石中的动物分化出了各种各样的现代动物。但是古生物学家们现在却认为所有的Tommotian化石都仅代表在寒武纪初期出现但到寒武纪结束时就消失了的特别生物。所以它们没有在现在动物中留下任何后代。
72.These fossil beds provide evidence of about 32 modern animal groups, plus about 20 other animal body forms that are so different from any modern animals that they cannot be assigned to any one of the modern groups.
这些化石层含有大约32种现代动物，还有大约20种与现在动物截然不同以致于不可能分类为任何一种现代动物的其他动物体。
73.With question such as these clearly before them, the scientists aboard the Glomar Challenger processed to the Mediterranean to search for the answers.
带着这些清楚摆在他们面前的问题，科学家们登上Glomar Challenger号前往地中海寻找答案。
74.In all probability it was the fertile plain of Latium, where the Latins who founded Rome originated, that created the habits and skills of landed settlement, landed property, landed economy, landed administration, and a land-based society.
完全也可能是Latium平原——拉丁人最初建立罗马的地方，早就了罗马人陆地定居、陆地财产、陆地经济、陆地行政以及以陆地基础社会的性格和技巧。
75.Agriculture seems to have reached these people from the Near East, since the first domesticated crops were millets and sorghums whose origins are not African but west Asian.
农业技术可能来自于近东最终为非洲人所知，因为最初驯化的农作物是起源于西亚而不是非洲的小米和高粱。
76.Most of Africa presents a curious case in which societies moved directly from a technology of stone to iron without passing through the intermediate stage of copper or bronze metallurgy, although some early copper-working sites have been found in West Africa.
大部分非洲表现出一种奇怪的现象，那就是他们社会直接从石器时代进步到铁器时代，而没有经过中间过渡的铜器或青铜器冶金术，尽管在西亚发现了一些早期使用铜器的地区。
77.They spoke a language, prior-Bantu ( Bantu means the people )which is the parent tongue of a language of a large number of Bantu languages still spoken throughout sub-Sahara Africa.
他们所说是前班图语,也就是现在仍然为广泛的撒哈拉沙漠南部非洲人所使用的班图语的源头。
78.Why and how these people spread out into central and southern Africa remains a mystery, but archaeologists believe that their iron weapons allowed them to conquer their hunting-gathering opponents, who still used stone implements.
这些人为什么扩散到非洲中部和南部？他们怎么迁徙的？仍然是迷。不过考古学家们相信他们的铁制武器足以让他们战胜那些靠采集打猎为生的敌人，因为这些人仍然利用石质工具。
79.With Cuicuilco eliminated as a potential rival, any one of a number of relatively modest towns might have emerged as a leading economic and political power in Central Mexico.
随着Cuicuilco失去了竞争能力，其他任何一个中等的城镇都可能成为墨西哥中部新一代政治经济中心。
80.The hard volcanic stone was a resource that had been in great demand for many years, at least since the rise of the Olmecs (a people who flourished between 1200 and 400 B.C.), and it apparently had a secure market.
那坚硬的火成岩在很多年内都是需求量极大的资源，至少从奥尔达克人(一个在公元前1200到400年间繁荣过的名族)的崛起之后就是这样了，显然它有着一个稳定的市场。
81.Moreover, recent research on obsidian tools found at Olmecs sites has shown that some of the obsidian obtained by the Olmecs originated near Teotihuacan.
再者，关于最近在Olmecs遗址中发掘的黑曜岩工具的研究表明，Olemcs所得到的部分黑曜石工具源自特奥蒂瓦坎地区。
82.The growing power of the elite, who controlled the economy, would give them the means to physically coerce people to move to Teotihuacan and serve as additions to the labor force.
而那些掌控者经济命脉的社会精英们的力量的增长就会为他们提供了种种方法以迫使人们移往特奥蒂瓦坎以充当额外的劳动力。
83.By measuring how many of these meteorites fall to Earth over a given period of time, scientists can estimate how long it might have taken to deposit the observed amount of lr in the boundary clay.
通过确定在一段给定时间内掉落在地球上的这种陨石的数量，科学家们就可以确定沉积隔层粘土的形成时间。
84.They bear a strong resemblance to river systems on Earth, and geologists think that they are dried-up beds of long-gone rivers that once carried rainfall on Mars from the mountains down into the valleys.
它们和地球上的河流系统非常相似，地质学家们认为它们是以前曾将火星上的雨水从高山携带到峡谷中的那些河流干涸后的遗迹。
85.Runoff channels on Mars speak of a time 4 billion years ago (the age of the Martian highlands), when the atmosphere was thicker, the surface warmer, and liquid water widespread.
火星上的径流通道存在于4百万年以前（就是火星高地的年龄），那时候火星的大气层更厚，地表更暖和，并且液态水分布很广。
86.The onrushing water arising from these flash floods likely also formed the odd teardrop-shaped islands(resembling the miniature versions seen in the wet sand of our beaches at low tide) that have been found on the plains close to the ends of the outflow channels.
由泛滥的洪水而产生的激流可能也形成奇怪的泪滴状小岛（就像是在低潮时湿沙地或海滩上看到的缩小版本一样），已经在靠近出流通道末尾处的平原上被看到。
87.Judging from the width and depth of the channels, the flow rates must have been truly enormous―perhaps as much as a hundred times greater than the 105 tons per second carried by the great Amazon river.
从这些通道的宽度和深度可判断，当时流速一定很大——有可能是亚马逊河的每秒钟105吨的流量的一百多倍.
88.A computer-generated view of the Martian north polar region shows the extent of what may have been an ancient ocean covering much of the northern lowlands.
一张关于火星北部极地地区的电脑图片说明有可能有一个古老的海洋覆盖了大部分北部的低洼处。
89.Proponents point to features such as the terraced beaches shown in one image, which could conceivably have been left behind as a lake or ocean evaporated and the shoreline receded.
反对者们指出照片里显示的台地“海滩”可以是由湖泊或者海洋蒸发干涸之后或者海退之后形成的。
90.But detractors maintain that the terraces could also have been created by geological activity, perhaps related to the geologic forces that depressed the Northern Hemisphere far below the level of the south, in which case they have nothing whatever to do with Martian water.
但是反对者认为这些台地也可能是由于地质活动造成的，即由于北半球的地质压力要远比南半球的小得多而造成的，在这种情况下，他们就和火星水系没有任何关系。
91.It has long been accepted that the Americas were colonized by a migration of peoples from Asia, slowly traveling across a land bridge called Beringia (now the Bering Strait between northeastern Asia and Alaska) during the last Ice Age.
这种观念被人们接受很长时间了：美洲被一群来自亚洲的移民殖民统治着，他们在上一个冰河时代缓慢的跨越了一个叫做白令的大陆桥（现在白令海峡位于东北亚和阿拉斯加之间）。
92. The first water craft theory about the migration was that around 11000-12000 years ago there was an ice-free corridor stretching from eastern Beringia to the areas of North America south of the great northern glaciers.
关于这些迁徙的第一个水路理论表明，大概在11000到12000年前，有一个不冻的走廊，它从白令海峡东部延伸到北美（大北部冰河的南部）。
93.But belief in this ice-free corridor began to crumble when paleoecologist Glen MacDonald demonstrated that some of the most important radiocarbon dates used to support the existence of an ice-free corridor were incorrect.
但是当生态学者Glen MacDonald证明一些用来支持不冻走廊存在的重要放射性碳时间不正确时，对于不冻走廊的信念就被粉碎了。
94.He theorized that with the use of watercraft, people gradually colonized unglaciated refuges and areas along the continental shelf exposed by the lower sea level.
他认为通过船只的使用，人们逐渐殖民到没有冰冻的地方以及沿着大陆架的、由于海平面较低而裸露出来的地区。
95.Fladmark's hypothesis received additional support from the fact that the greatest diversity in Native American languages occurs along the west coast of the Americans, suggesting that this region has been settled the longest.
Fladmark的假设从一个事实那得到了更多的支持，因为美国本土语言的最大多样性出现在西海岸沿岸，这就表明这个地区是人类定居时间最早的。
96.Vast areas along the coast may have been deglaciated beginning around 16,000 years ago, possibly providing a coastal corridor for the movement of plants, animals, and humans sometime between 13,000 and 14,000 years ago.
沿海的辽阔地区的冰川在大约16000年前开始融化，这就为13000前 到14000年前的某一段时间内植物、动物和人类的迁移提供了一个海岸走廊。
97.The coastal hypothesis has gained increasing support in recent years because the remains of large land animals, such as caribou and brown bears, have been found in southeastern Alaska dating between 10,000 and 12,500 years ago.
海岸走廊假设近些年得到了越来越多的支持，因为一些大型动物（比如北美驯鹿，棕熊）的遗迹出现在阿拉斯加东南部地区，其时间为10000年到12500年之前。
98.Fladmark and others believe that the first human colonization of America occurred by boat along the Northwest Coast during the very late Ice Age, possibly as early as 14,000 years ago.
Fladmark和其他科学家都认为人类第一次乘船沿着西北岸到达美洲发生在冰河时代的晚期，可能早达14000年以前。
99.The most recent geologic evidence indicates that it may have been possible for people to colonize ice-free regions along the continental shelf that were still exposed by the lower sea level between 13,000 and 14,000 ago.
多数最新的地质资料表明：13000年 至 14000年前，人们殖民因低海平面而裸露的大陆架沿岸的无冰区域是可能的。
100.They were concerned that many would be drawn to these new, refreshing conceptions of teaching only to find that the void between the abstractions and the realities of teacher reflection is too great to bridge.
他们担心很多人可能认为沉浸在这种全新的教育概念中的结果就是，发现教师反思的抽象概念和现实之间的鸿沟太大而无法逾越。
101.Further observation revealed the tendency of teachers to evaluate events rather than review the contributory factors in a considered manner by, in effect, standing outside the situation.
更深的研究发现教师们更愿意评价事件而不是站在事件之外洞察一个事件的促进因素。
102.The researchers estimate that the initial training of the same teachers to view events objectively took between 20 and 30 hours, with the same number of hours again being required to practice the skills of reflection.
研究者认为训练同一个教师使他客观的看待事情需要大约20到30小时，而反思技巧的练习同样需要这么多时间。
103.The teachers in the program described how they found it difficult to put aside the immediate demands of others in order to give themselves the time they needed to develop their reflective skills.
项目中的教师们抱怨说让他们放弃别人当时的要求而为自己腾出时间去提升自己的反思能力是很困难的。
104.Support and encouragement were also required to help teachers in the program cope with aspects of their professional life with which they were not comfortable.
项目中的教师同样需要支持和鼓励以帮助他们去应付他们职业生活中的不如意的方面。
105.The fungi absorb moisture and mineral salts from the rocks, passing these on in waste products that nourish algae.
真菌从岩石中吸收水分和矿物盐，并将这些作为代谢废物为海藻施肥。
106.Lichens helped to speed the decomposition of the hard rock surfaces, preparing a soft bed of soil that was abundantly supplied with minerals that had been carried in the molten rock from the bowels of Earth.
地衣有利于加速坚硬的岩石表面的分解，并产生了一层柔软的土壤，这些土壤可以提供熔融岩石含有的来自地球内部的丰富的矿物质。
107.By means of these seeds, plants spread more widely to new locations, even to isolated islands like the Hawaiian archipelago, which lies more than 2,000 miles west of California and 3,500 miles east of Japan.
借助这些种子，植物传播到更远的地方，甚至是像夏威夷群岛这样的孤立的群岛上。夏威夷群岛位于加利福利亚以西2000英里和日本以东3500英里。
108.Although we now tend to refer to the various crafts according to the materials used to construct them--clay, glass, wood, fiber, and metal--it was once common to think of crafts in terms of function, which led to their being known as the "applied arts."
在现代，人们将根据
工艺
钢结构制作工艺流程车尿素生产工艺流程自动玻璃钢生产工艺2工艺纪律检查制度q345焊接工艺规程
品的制造材质对他们进行分类，如陶土，玻璃，木头，纤维还有金属。但最初人们根据工艺品的功能将他们通通定义为“实用工艺品”。
109.Since the laws of physics, not some arbitrary decision, have determined the general form of applied-art objects, they follow basic patterns, so much so that functional forms can vary only within certain limits.
自然规律决定了实用工艺品的一般形式，而不是武断的结论决定的，它们遵循基本的样式，以至于它们的功能不会变化太大。
110.That this device was a necessary structural compromise is clear from the fact that the cannonball quickly disappeared when sculptors learned how to strengthen the internal structure of a statue with iron braces (iron being much stronger than bronze).
当雕塑家学会如何了用铁支架加强雕塑的内部结构后（铁比青铜更结实），就不再使用金属球了，由此看来，铁球的使用是对于必要结构性的妥协。
111.Even though the fine arts in the twentieth century often treat materials in new ways, the basic difference in attitude of artists in relation to their materials in the fine arts and the applied arts remains relatively constant.
尽管在20世纪纯工艺品的制作通常采用新的制造工艺，人们对两种工艺品的基本态度仍然保持对立。
112.Pakicetus was found embedded in rocks formed from river deposits that were 52 million years old.
Pakicifus是在一条河的沉积岩中发现的，这条河有5200万年的历史，离古地中海不远
113.The structure of the backbone shows, however, that Ambulocetus swam like modern whales by moving the rear portion of its body up and down, even though a fluke was missing.
不过，从Ambulocetus的脊椎结构上可以看出，即使缺少尾片，它们也能像现代鲸鱼那样通过身体背部的上下摆动来游走。
114.The impact of raindrops on the loose soil tends to transfer fine clay particles into the tiniest soil spaces, sealing them and producing a surface that allows very little water penetration.
雨水对与松动的土壤的作用表现在可以将性装良好的泥土颗粒转移到狭小的沙间间隙中，然后封住间隙，形成几乎不允许水分的渗透的表面
115.The gradual drying of the soil caused by its diminished ability to absorb water results in the further loss of vegetation, so that a cycle of progressive surface deterioration is established.
蓄水能力下降的土壤变得越来越干燥进一步造成植被的减少，以致于建立了一个地表逐渐恶化的循环
116.During the dry periods that are common phenomena along the desert margins, though, the pressure on the land is often far in excess of its diminished capacity, and desertification results.
然而，在沙漠边缘最常见的干旱时期，给予土地的压力常常超过了它本身脆弱的能力，最后沙漠化就产生了。
117.The increased pressures of expanding populations have led to the removal of woody plants so that many cities and towns are surrounded by large areas completely lacking in trees and shrubs.
人口扩展压力的增加导致木本植物被砍伐，以助于很多城市和城镇的周边很大面积几乎看不到树木和灌木丛。
118.The increasing use of dried animal waste as a substitute fuel has also hurt the soil because this valuable soil conditioner and source of plant nutrients is no longer being returned to the land.
大量使用干燥动物粪便作为替代燃料伤害到土壤，因为这些有价值的土壤护理剂和植物养料的来源都不能回归到土地中了。
119.In areas where considerable soil still remains, though, a rigorously enforced program of land protection and cover-crop planting may make it possible to reverse the present deterioration of the surface.
那些仍然还有可观土壤量的地区，制定严格的土地保护政策和地表植被种植仍然有可能逆转现在地面的毁坏情况。
120.The cinema did not emerge as a form of mass consumption until its technology evolved from the initial "peepshow" format to the point where images were projected on a screen in a darkened theater.
电影院的播放技术从最初的西洋镜形式演变为将影像投影到幽暗的影院屏幕，这一转变使得电影院大众化消费成为可能。
121.It was designed for use in Kinetoscope parlors, or arcades, which contained only a few individual machines and permitted only one customer to view a short, 50-foot film at any one time.
这种放映机仅适用于活动电影放映室或电影娱乐城，它里面仅包含少量的独立播放器，每次仅允许一个顾客观看一部50张胶卷的小短片。
122.In the phonograph parlors, customers listened to recordings through individual ear tubes, moving from one machine to the next to hear different recorded speeches or pieces of music.
在留声机播放厅中，顾客们通过独立的耳管听取已经录制好的声音，从一台机器换到另一台听取不同演讲或音乐的录音。
123.He refused to develop projection technology, reasoning that if he made and sold projectors, then exhibitors would purchase only one machine--a projector--from him instead of several.
他不愿研究投影技术，因为他认为如果研发并且销售投影机，电影放映者就只会买一台投影机而不是几台。
124.But the movies differed significantly from these other forms of entertainment, which depended on either live performance or (in the case of the slide-and-lantern shows) the active involvement of a master of ceremonies who assembled the final program.
电影与这些娱乐形式明显的不同点是，电影无需依赖现场表演，也不需要串联全场节目的主持人的积极参与（例如胶片演示）。
125.Although early exhibitors regularly accompanied movies with live acts, the substance of the movies themselves is mass-produced, prerecorded material that can easily be reproduced by theaters with little or no active participation by the exhibitor.
尽管早期的电影放映者通常在电影放映时伴有现场表演，但是电影本身的内容是影院事先大量录制下来的，这些材料能在没有表演者或者表演者较少参与的情况在电影院中轻松地再现。
126.Even though early exhibitors shaped their film programs by mixing films and other entertainments together in whichever way they thought would be most attractive to audiences or by accompanying them with lectures, their creative control remained limited.
即便这样，早期的电影放映者还是将电影和其它娱乐节目或者演讲结合在一起，他们认为用这样的方法能最大限度的吸引观众，他们管理的创造力还是非常有限的。
127.With the advent of projection, the viewer's relationship with the image was no longer private, as it had been with earlier peepshow devices such as the Kinetoscope and the Mutoscope, which was a similar machine that reproduced motion by means of successive images on individual photographic cards instead of on strips of celluloid.
伴随投影机的到来，电影不在属于个别人的消费品。就像之前西洋镜时代的播放设备，如活动电影播放机和早期电影播放机，早期电影播放机播放的都是一系列独立的图像而不是胶片，把单个摄影卡上的图片串联起来形成影像。
128.At the same time, the image that the spectator looked at expanded from the minuscule peepshow dimensions of 1 or 2 inches (in height) to the life-size proportions of 6 or 9 feet.
与此同时，观众所看到的图像大小也从狭小的1英寸或2英寸西洋镜高度扩展到与实物状的6英尺或9英尺。
129.Those individuals who possess characteristics that provide them with an advantage in the struggle for existence are more likely to survive and contribute their genes to the next generation.
那些拥有竞争优势的个体更容易存活，并且会将它们有利于生存竞争的基因遗传给下一代。
130.Because aggressive individuals are more likely to survive and reproduce, whatever genes are linked to aggressive behavior are more likely to be transmitted to subsequent generations.
拥有侵略性特质的个体更容易存活和繁殖，因此，与侵略性行为相关的各种基因遗传给下一代的可能性更大。
131.Children normally desire to vent aggressive impulses on other people, including their parents, because even the most attentive parents cannot gratify all of their demands immediately.
孩子们时常想对包括他们父母在内的其他人发泄侵略性冲动的情感，因为即使是最周全的父母也无法做到立即满足孩子的所有要求。
132.People decide whether they will act aggressively or not on the basis of factors such as their experiences with aggression and their interpretation of other people's motives.
一个人是否采取出侵略性行动取决于以下因素，他们进行侵略性攻击的经历，对他人动机的解读等。
133.Factory life necessitated a more regimented schedule, where work began at the sound of a bell and workers kept machines going at a constant pace.
工厂化生产方式要求工人们加强之前没有的时间观念，要求他们严格遵守工作时间的安排，铃声响起，工人们开始操控机器稳速运转。
134.One mill worker who finally quit complained revealingly about "obedience to the ding-dong of the bell-just as though we are so many living machines."
一名最终辞职的磨坊工人袒露真情地抱怨道：“让我们听从于叮叮当当的钟表，简直就把我们当成了活生生的机器。”
135.Unlike artisan workshops in which apprentices worked closely with the masters supervising them, factories sharply separated workers from management.
和手工作坊里徒弟与监督他们的师傅之间的密切工作关系不同，工厂将工人阶层与管理层明显地区分开。
136.More than a decade of agitation did finally bring a workday shortened to 10 hours to most industries by the 1850s, and the courts also recognized workers' right to strike, but these gains had little immediate impact.
直到19世纪50年代，超过十年的抗争最终使得大多数行业的工作时间缩短至10小时，法院也承认了工人罢工的权利，但这些权利的影响并没有立即显现。
137.When not in use, the fins are tucked into special grooves or depressions so that they lie flush with the body and do not break up its smooth contours.
当鱼儿们不使用鱼鳍时，会将它们折回到特殊的沟槽或者凹陷的地方，与身体保持同一平面，以维持它们平滑的外形。
138.They must also keep swimming to keep from sinking, since most have largely or completely lost the swim bladder, the gas-filled sac that helps most other fish remain buoyant.
它们必须通过游泳而保持不下沉。大部分金枪鱼很大程度上已经丧失了其他鱼类用于保持漂浮状态的鱼鳔，或者说已经完全丧失
139.The development of the modern presidency in the United States began with Andrew Jackson who swept to power in 1829 at the head of the Democratic Party and served until 1837.
美国现代总统
制度
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的发展是从安德鲁杰克逊开始的。这位民主党领导人在1829年掌权，直至1837年卸任。
140.The Fore also displayed familiar facial expressions when asked how they would respond if they were the characters in stories that called for basic emotional responses.
Fore还给出了一些人们熟悉的基本表情，要求答卷者回答如果你是故事中的人物你会作出哪种基本表情？
141.Ekman and his colleagues more recently obtained similar results in a study of ten cultures in which participants were permitted to report that multiple emotions were shown by facial expressions.
埃克曼和他的同事们从近期的一项统计中得出了相同的结论，他们对来自10个不同文化背景的参与者们进行了调查，参与者可以通过多种面部表情传达复杂的情绪。
142.According to this hypothesis, signals from the facial muscles ("feedback”) are sent back to emotion centers of the brain, and so a person's facial expression can influence that person's emotional state.
根据这个假设，脸部肌肉承载的信号会被传至大脑的控制情绪的部位中，因此人类面部表情会影响他们的情绪。
143.But when the emotion that leads to stiffening the lip is more intense, and involves strong muscle tension, facial feedback may heighten emotional response.
但是，当内心情绪导致僵硬的嘴唇更加紧张时，面部表情强有力的收缩很有可能会加剧内心的情绪反应。
144.Hills and mountains are often regarded as the epitome of permanence, successfully resisting the destructive forces of nature, but in fact they tend to be relatively short-lived in geological terms.
山峰和山脉因为能够经受得住自然的洗礼，通常被认作是永恒的代名词，但地质学的角度上来说，他们的存在实际上从是相对比较短暂的。
145.About 400 million years ago, when the present-day continents of North America and Europe were joined, the Caledonian mountain chain was the same size as the modern Himalayas.
在大约400万年前，当今天的北美和欧洲大陆相结合的时候，加勒多尼亚山脉与现今的喜马拉雅山脉同样雄伟。
146.Glaciers may form in permanently cold areas, and these slowly moving masses of ice cut out valleys, carrying with them huge quantities of eroded rock debris.
冰川在长期寒冷的区域形成，这些缓慢移动的大量冰块带着大量的腐蚀岩屑阻断了山谷。
147.Fuller devised a type of dance that focused on the shifting play of lights and colors on the voluminous skirts or draperies she wore, which she kept in constant motion principally through movements of her arms, sometimes extended with wands concealed under her costumes.
Fuller
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了一种注重灯光变换和她所穿的大体积的裙子或布料的颜色的舞蹈，所以她的舞姿则主要体现在上肢动作，而有些时候她的服装的体积是需要用隐藏在下面的棍状物体来填充实现的。
148.Although her early theatrical career had included stints as an actress, she was not primarily interested in storytelling or expressing emotions through dance; the drama of her dancing emanated from her visual effects.
虽然在她早期的舞台事业里体现了作为一名艺术家的一些约束，她的主要精力并没有放在通过舞蹈来传递故事或感情上，而是通过视觉效应散发出她舞蹈的戏剧性。
149.Although she discovered and introduced her art in the United States, she achieved her greatest glory in Paris, where she was engaged by the Folies Bergere in 1892 and soon became “La Loie,” the darling of Parisian audiences.
尽管她是在美国找到并呈现了她的艺术，她最大的成就在巴黎，在1892年她被Folies Bergere（一个巴黎剧院）所雇佣,而不久变成“La Loie”----巴黎观众的宠儿。
150.Her interest in color and light paralleled the research of several artists of the period, notably the painter Seurat, famed for his Pointillist technique of creating a sense of shapes and light on canvas by applying extremely small dots of color rather than by painting lines.
她对色彩和灯光的研究与当时几位艺术家相媲美，比如点彩派画家Seurat，他是以在画布上运用极其细微的点不是线条来创造形状和光泽而著名的。
151.Although she gave little thought to music in her earliest dances, she later used scores by Gluck, Beethoven, Schubert, Chopin, and Wagner, eventually graduating to Stravinsky, Faure, Debussy, and Mussorgsky, composers who were then considered progressive.
尽管在她在早期舞蹈作品中，没有花太多心思在音乐上，但随后她使用了Gluck, Beethoven, Schubert, Chopin,和Wagner的乐曲，最后则变成了采用在当时被认为进步的一些作曲家的曲子，像Stravinsky, Fauré, Debussy, 和Mussorgsky。
152.Always open to scientific and technological innovations, she befriended the scientists Marie and Pierre Curie upon their discovery of radium and created a Radium Dance, which simulated the phosphorescence of that element.
因为总是对科技创新抱有很开放的态度，她与科学家Marie和Pierre Curie在镭的研究中成为了朋友，并创造出了作品镭来模仿该元素的磷光。
153.Although she is remembered today chiefly for her innovations in stage lighting, her activities also touched Isadora Duncan and Ruth St. Denis, two other United States dancers who were experimenting with new types of dance.
尽管她主要是被她所带来的舞台灯光革新所为人们熟知的，但她的事迹也与Isadora Duncan和Ruth St. Denis, 这两个当时尝试新型舞蹈的舞者有关。
154.They may change color with changing light conditions and cloud cover, glowing pink or gold in the morning or evening light, but this color change is generally related to the low angle of the Sun above the horizon.
在不同情况的光和云量下，它们的颜色呈现可能会随之不同，如在早晨和傍晚的阳光下所呈现的耀眼的粉色或金色，但这个颜色变化大致与太阳位于海平面上的低角度有关。
155.One explanation for green icebergs attributes their color to an optical illusion when blue ice is illuminated by a near-horizon red Sun, but green icebergs stand out among white and blue icebergs under a great variety of light conditions.
对于绿冰山的颜色的一个解释是由于纯冰被接近海平面的太阳所照射而造成的错觉，但是绿冰山在很多不同状态的阳光下都能从白色和蓝色冰山中区分出来。
156.The scientists concluded that green icebergs form when a two-layer block of shelf ice breaks away and capsizes (turns upside down), exposing the bubble-free shelf ice that was formed from seawater.
科学家总结出，绿冰的构成是在两层的架冰分开并翻转过来时，暴露出的没有气泡的海水冰。
157.A green iceberg that stranded just west of the Amery Ice Shelf showed two distinct layers: bubbly blue-white ice and bubble-free green ice separated by a one-meter-long ice layer containing sediments.
个在Amery Ice Shelf西部滞留的绿冰山呈现出了两个明显的层：含有气泡的白蓝色冰，和没有气泡的绿色冰，它们中间是由1米长的带有沉积物的冰分隔开的。
158.For example, some early societies ceased to consider certain rites essential to their well-being and abandoned them, nevertheless, they retained as parts of their oral tradition the myths that had grown up around the rites and admired them for their artistic qualities rather than for their religious usefulness.
例如，一些早期社会的人们认为有的仪式对他们的幸福生活来说不再是必需品，并且取消了那些仪式。虽然如此，人们还是保留了那些口头传述故事的传统并且热爱从这些仪式里发展起来的神话，出于它们的艺术性，而不是宗教原因。
159.Famous explorers of the north American frontier, Lewis and Clark had experienced great difficulty finding game west of the Rockies and not until the second of December did they kill their first elk.
著名的北美探险先驱者刘易斯和克拉克在落基山西部经历种种困难，并且直到第二年十二月他们才杀死了第一只麋鹿。
160.We might expect that early artistic efforts would be crude, but the cave paintings of Spain and southern France show a marked degree of skill. So do the naturalistic paintings on slabs of stone excavated in southern Africa.
虽然，我们可能会认为早期的艺术成就都是不成熟的，但西班牙与法国南部的岩洞画显示出了高超的技艺，在非洲南部发掘出的自然石板画也是如此。
161.Not only could Smith identify rock strata by the fossils they contained, he could also see a pattern emerging: certain fossils always appear in more ancient sediments, while others begin to be seen as the strata become more recent.
史密斯不仅可以通过岩石中包含的化石来识别地层，而且可以看出他们显露出来的模式：一些特定的化石往往出现在更为久远的沉积物当中，而其他的化石则可以在距今年代较近的地层中发现。
162.Only recently have investigators considered using these plants to clean up soil and waste sites that have been contaminated by toxic levels of heavy metals--an environmentally friendly approach known as phytoremediation.
直到最近研究者才考虑用这些植物来清理已经被有毒重金属污染的土壤和废弃物物处理点——一种被称为植物修复的环境友好方法。
163."Had the Greeks held novelty in such disdain as we," asked Horace in his Epistle, "what work of ancient date would now exist?"
如果希腊人跟我们一样鄙视创新,。。。。，那(希腊的)古迹还会存在吗?
164.Nor did the Whigs envision any conflict in society between farmers and workers on the one hand and businesspeople and bankers on the other.
自由党并没有预测到社会上存在的工人与农民，商人与银行家之间的冲突。
165.Interbedded with the salt were thin layers of what appeared to be windblown silt.
跟结晶盐相互嵌在一起的薄层像是被风吹起的泥沙层。
166.From this arose the Roman genius for military organization and orderly government.
在此基础上也产生了罗马人的军事组织和政府管理的才能。
167.With the loss of personal freedom also came the loss of standing in the community.
失去了个人自由也会造成在社会中失去身份（地位）。
168.Only when it has been chewed up and digested almost to a liquid can the food pass through the rumen and on through the gut.
只有当食物在经过咀嚼和消化的过程变成近似液体的时候，它才可能通过瘤胃并进入和通过肠胃。
169.The commonest spaces are those among the particles and grains and tiny pebbles of loose, unconsolidated sand and gravel.
松散的砂子和砾石间有许多颗粒和小石子，他们之间的空隙是最常见的储存地下水的空间。
170.The water was always laden with pebbles, gravel, and sand, known as glacial outwash, that was deposited as the flow slowed down.
水里总会携带些石子、砾石和沙石，这就是所谓的冰河期的冰水沉积，这些颗粒会随着水流的减速而沉淀。
171. One, set forth by Aristotle in the fourth century B.C., sees humans as naturally imitative—as taking pleasure in imitating persons, things, and actions and in seeing such imitations.
首先，亚里士多德在公元前4世纪提出，人们天生好模仿，并从模仿他人、事物和动作以及观看模仿中获得乐趣。
172.The most widely accepted theory, championed by anthropologists in the late nineteenth and early twentieth centuries, envisions theater as emerging out of myth and ritual.
9世纪末20世纪初为人类学家们所拥护的一种理论得到了世人的广泛认同；这种观点认为戏剧起源于神话和宗教仪式。
173.In order for the structure to achieve the size and strength necessary to meet its purpose, architecture employs methods of support that, because they are based on physical laws, have changed little since people first discovered them-even while building materials have changed dramatically.
建筑结构必须达到大小和强度的要求，以实现必要的建筑目的，因此建筑学上采用一些支撑的方法，这些方法都是以物理定律为基础的，尽管建筑材料已经发生了翻天覆地的变化，这些支撑的方法却自人们发现它们以来就鲜有变化。
174.Estimates indicate that the aquifer contains enough water to fill Lake Huron, but unfortunately, under the semiarid climatic conditions that presently exist in the region, rates of addition to the aquifer are minimal, amounting to about half a centimeter a year.
据估计，奥加拉拉蓄水层的含水量足以填满休伦湖，但不幸的是，在目前该地区半干旱的气候条件下，奥加拉拉蓄水层的蓄水能力极低，每年仅半厘米左右。
175.Modern irrigation devices, each capable of spraying 4.5 million liters of water a day, have produced a landscape dominated by geometric patterns of circular green islands of crops.
日喷水量达到4500000升的现代灌溉设备，形成了一个圆形绿岛作物为主的景观。
176.This unprecedented development of a finite groundwater resource with an almost negligible natural recharge rate--that is, virtually no natural water source to replenish the water supply--has caused water tables in the region to fall drastically.
考虑到几乎没有补充率（实质上没有自然水资源进行补充），这种有限地下水资源前所未有的发展已经引起了该地区地下水位的急剧下降。
177.It is possible that tubes made from animal bones were used for spraying because hollow bones, some stained with pigment, have been found nearby.
喷洒的工具很可能用的是动物骨骼制成的管子，因为在画的附近发现了一些沾有颜料的空心骨骼。
178.A third opinion takes psychological motivation much further into the realm of tribal ceremonies and mystery: the belief that certain animals assumed mythical significance as ancient ancestors or protectors of a given tribe or clan.
第三种意见把心理动机上升到部落仪式和神话的层面：他们相信某些动物拥有神秘的重要性，它们是某个特定部落或种族的古老祖先或守护神。
179.Advocates for this opinion point to reports from people who have experienced a trance state, a highly suggestive state of low consciousness between waking and sleeping.
这个观点的提倡者们提供了一份人类经历昏迷状态的
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，昏迷是一种介于清醒和睡眠之间的低意识的状态。
180.The other species, the Columbian white-tailed deer, in earlier times was common in the open prairie country, it is now restricted to the low, marshy islands and flood plains along the lower Columbia River.
另一种哥伦比亚白尾鹿，从前在开阔的草原上很常见，而现在只能在低矮的沼泽岛屿地带和哥伦比亚河下游的河滩地区才能看到它们。
181.Hulmut Buechner(1953), in reviewing the nature of biotic changes in Washington through recorded time, says that "since the early 1940s, the state has had more deer than at any other time in its history, the winter population fluctuating around approximately 320,000 deer (mule and black-tailed deer), which will yield about 65,000 of either sex and any age annually for an indefinite period."
野生动物学家赫尔穆特·布希纳（1953）通过已有记录评论了华盛顿地区生物的自然变化，他说：二十世纪40年代早期，美国拥有比以往任何历史时期都多的鹿群，鹿群冬季的数量在接近320000只鹿（杂交和黑尾鹿）左右波动，在此之后的每一年不同年龄段的公鹿和母鹿数量分别会增加至65000只。
182. In addition to finding an increase of suitable browse, like huckleberry and vine maple, Arthur Einarsen, longtime game biologist in the Pacific Northwest, found quality of browse in the open areas to be substantially more nutritive.
以便他们去寻找更适合的嫩叶，比如越橘类和枫叶,太平洋西北的生物学家亚瑟·埃纳森发现在空旷地区的高质量的嫩叶大部分都是很有营养的.
183.She rejected the technical virtuosity of movement in ballet, the most prestigious form of theatrical dance at that time, perhaps because her formal dance training was minimal.
她没有采用在当时的舞台式舞蹈上声望很高的高技术含量的芭蕾动作，原因可能是她所接受的正式舞蹈培训太少了。
184. Continued sedimentation—the process of deposits' settling on the sea bottom—buries the organic matter and subjects it to higher temperatures and pressures, which convert the organic matter to oil and gas.
持续的沉积——堆积物沉积到海底的过程将有机物埋在海底使之受到海底温度、高压的影响，最终转变成油和气体。
185. Spillage from huge oil-carrying cargo ships, called tankers, involved in collisions or accidental groundings (such as the one off Alaska in 1989) can create oil slicks at sea.
运载石油的油轮在发生碰撞或意外搁浅（如在1989年阿拉斯加发生的油轮搁浅）的情况下，石油泄露会使得海上产生浮油。
186.This “atmospheric engine” improved by his partner, Thomas Newcomen, embodied revolutionary principles, but it was so slow and wasteful of fuel that it could not be employed outside the coal mines for which it had been designed.
这一由他的同伴托马斯纽科门对其进行改良的“大气引擎”，被赋予了革命性的工作原理。但其效率低下且浪费燃料，无法在煤矿以外的地区使用，这与最初的设计期望背道而驰。
187. In 1815 he published the first modern geological map, A Map of the Strata of England and Wales with a Part of Scotland," a map so meticulously researched that it can still be used today.
1815年，他绘制了第一张现代地质学地图——英格兰威尔士及苏格兰部分地区地层地图，这张地质地图绘制得非常精确，直到现在仍有参考价值。
188. Even without the problem of regional differences, rocks present a difficulty as unique time markers Quartz is quartz-a silicon ion surrounded by four oxygen ions-there’s no difference at all between two-million-year-old Pleistocene quartz and Cambrian quartz created over 500 million years ago．
即便排除区域差异的影响，人们面对岩石，还是存在一道难题，石英作为一种独特的时间标记——四个氧离子包围一个硅离子的化合物，而两百万年前的更新世石英和五亿年前形成的寒世纪的石英并无差别，这让人们束手无措。
189. Limestone may be found in the Cambrian or-300 million years later-in the Jurassic strata but a trilobite—the ubiquitous marine arthropod that had its birth in the Cambrian—will never be found in Jurassic strata, nor a dinosaur in the Cambrian.
人类有可能在侏罗纪时期的地层中发现寒世纪或者三亿年后的石灰岩，但绝不可能在侏罗纪时期地层中发现三叶虫化石（三叶虫是寒世纪非常普遍的水生节肢动物），也不可能发现寒世纪时期的恐龙化石。
190.While rock between two consistent strata might in one place be shale and in another sandstone, the fossils in that shale or sandstone were always the same.
在同层的地层中发现的岩石可能在这片地层中属于泥板岩，而在另一片地层中可能是砂岩，而在那些泥板岩或者砂岩中的化石往往都是一样的。
191.Nor does the hypothesis that infantile amnesia reflects repression--or holding back--of sexually charged episodes explain the phenomenon．
那些假设婴幼儿健忘症反映了孩子们对充满性欲的插曲的压制和隐藏，同样也解释不通。
192.Thus, all three explanations--physiological maturation, hearing and producing stories about past events，and improved encoding of key aspects of events--seem likely to be involved in overcoming infantile amnesia．
综上所述，生理上的成熟、听故事和讲故事以及改进对事件关键信息的编码都有助于克服婴幼儿遗忘症。
193. Acroponics, a technique in which plants are suspended and the roots misted with a nutrient solution, is another method for growing plants without soil.
气培法，一种把植物悬挂起来，将其根部喷上营养液，是另外一种无土栽培的方法。
194.Saline soils, which have high concentrations of sodium chloride and other salts, limit plant growth, and research continues to focus on developing salt-tolerant varieties of agricultural crops.
含有高浓度的氯化钠和其他盐类的盐碱土壤抑制植物生长，于是研究继续集中开发耐盐农作物品种。
195.After several years of cultivation and harvest, the site would be restored at a cost much lower than the price of excavation and reburial, the standard practice for remediation of contaminated soils.
经过几年的种植和收割，该污染点将被修复，而其造价远比修复污染土壤的
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做法——挖掘和填埋来得低。
196.The culture of that time, based on archaeology and linguistic reconstruction, is assumed to have had a broad inventory of cultivated plants including taro, yarns, banana, sugarcane, breadfruit, coconut, sago, and rice.
通过考古学和语言学的重建发现，那个时候的文明拥有广泛的植物储存，包括芋头、纱、香蕉、甘蔗、面包果树、椰子、西米和稻米。
197.As a result of crustal adjustments and faulting, the Strait of Gibraltar, where the Mediterranean now connects to the Atlantic, opened, and water cascaded spectacularly back into the Mediterranean.
作为地壳调整和断层作用的结果，现在连接地中海和大西洋的直布罗陀海峡打开了，水流像瀑布一样壮观地涌回地中海。
198.These peoples settled at first in scattered hunting-and-gathering bands, although in some places near lakes and rivers, people who fished, with a more secure food supply, lived in larger population concentrations.
这些部落起初分散的定居，并仍靠打猎和采集维生，尽管是在靠近湖泊和河流的地区人们以捕鱼为业，有较稳定的食物供给，聚集了较多的人口。
199. Their migration may have been set in motion by an increase in population caused by a movement of peoples fleeing the desiccation or drying up, of the Sahara.
为了逃避撒哈拉沙漠的不断干旱，人们迁徙到尼日尼亚东部，使这里的人口增多，于是这里的人们也接着迁徙。
200. It seems likely that Teotihuacán's natural resources—along with the city elite's ability to recognize their potential—gave the city a competitive edge over its neighbors.
很可能是特奥蒂瓦坎的自然资源，和精英们重组它们的才能，给予这座城市以与其邻居们抗衡的力量。
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