【课文】 First listen and then answer the following question. 听录音,然后回答以下问题。 What does a pen have to do to record on paper the vibrations generated by an earthquake? An earthquake comes like a thief in the night, without warning. It was necessary, therefore, to invent instruments that neither slumbered nor slept. Some devices were quite simple. One, for instance, consisted of rods of various lengths and thicknesses which would stand up on end like ninepins. When a shock came, it shook the rigid table upon which these stood. If it were gentle, only the more unstable rods fell. If it were severe, they all fell. Thus the rods, by falling, and by the direction in which they fell, recorded for the slumbering scientist the strength of a shock that was too weak to waken him, and the direction from which it came. But instruments far more deliecate than that were needed if any really serious advance was to be made. The ideal to be aimed at was to devise an instrument that could record with a pen on paper, the movements of the ground or of the table as the quake passed by. While I write my pen moves, but the paper keeps still. With practice, no doubt, I could in time learn to write by holding the pen still while the paper moved. That sounds a silly suggestion, but that was precisely the idea adopted in some of the early instruments (seismometers) for recording earthquake waves. But when table, penholder and paper are all moving, how is it possible to write legibly? The key to a solution of that problem lay in an everyday observation. Why does a person standing in a bus or train tend to fall when a sudden start is made? It is because his feet move on , but his head stays still. A simple experiment will help us a little further. Tie a heavy weight at the end of a long piece of string. With the hand held high in the air, hold the string so that the weight nearly touches the ground. Now move the hand to and fro and around but not up and down. It will be found that the weight moves but slightly or not at all. Imagine a pen attached to the weight in such a way that its point rests upon a piece of paper on the floor. Imagine an earthquake shock shaking the floor, the paper, you and your hand. In the midst of all this movement, the weight and the pen would be still. But as the paper moved from side to side under the pen point, its movement would be recorded in ink upon its surface. It was upon this principle that the first instruments were made, but the paper was wrapped round a drum which rotated slowly. As long as all was still, the pen drew a straight line, but while the drum was being shaken, the line that the pen was drawing wriggled from side to side. The apparatus thus described, however, records only the horizontal component of the wave movement, which is, in fact, much more complicated. If we could actually see the path described by a particle, such as a sand grain in the rock, it would be more like that of a bluebottle path described by a particle, such as a sand grain in the rock, it would be more like that of a bluebottle buzzing round the room; it would be up and down, to and fro and from side to side. Instruments have been devised and can be so placed that all three elements can be recorded in different graphs. When the instrument is situated at more than 700 miles from the earthquake centre, the graphic record shows three waves arriving one after the other at short intervals. The first records the arrival of longitudinal vibrations. The second marks the arrival of transverse vibrations which travel more slowly and arrive several minutes after the first. These two have travelled through the earth. It was from the study of these that so much was learnt about the interior of the earth. The third, or main wave, is the slowest and has travelled round the earth through the surface rocks. H.H,SWINNERTON The Earth beneath Us 【New words and expressions 生词和短语】 earthquake n. 地震 slumber v. 睡眠 ninepin n. 九柱戏中的木柱 rigid adj. 坚硬的 delicate adj. 灵感的 seismometer n. 地震仪 penholder n. 笔杆 legibly adv. 字迹清楚地 drum n. 鼓状物 wriggle v. 扭动 bluebottle n. 绿头苍蝇 graph n. 图表 graphic adj. 图示的 longitudinal adj. 纵向的 transverse adj. 横向的 【课文注释】 1.slumber v.睡眠 例句:She fell into restful slumber. 她进入宁静的安眠之中。 Allow no sleep to your eyes, no slumber to your eyelids. 不要容你的眼睛睡觉,不要容你的眼皮打盹。 【词义辨析】 sleep, doze, nap, slumber 这些动词均含“睡”之意。 sleep : 普通用词,指一般的睡眠。可用作引申指长眠或静止不动。 doze : 多用于口语中,指轻微的小睡或处于半睡状态。 nap : 指白天的小睡。 slumber : 多指人安详地或长时间地睡。 2. stand up on end 竖立着 3.rigid adj.坚硬的;刻板的 例句:The tent has a rigid support. 帐篷有一个坚硬的支柱。 He's very rigid in his ideas. 他的想法非常固执。 【词义辨析】 rigid, strict, rigorous这些形容词均含“刻板的,严格的”之意。 rigid: 指没有灵活性、机动性。 strict: 指在行为规则上要求严格。 rigorous: 侧重指严格到毫不宽容的地步。 4.The ideal to be aimed at 理想的目标 5.devise vt. 设计, 发明, 遗赠 例句:This time we'll devise a better solution. 这次我们将设计一种新的解决方案。 He devised a new type of transistor. 他发明了一种新的晶体管。 【词义辨析】 devise, conceive, formulate 这些动词的均含“设计、设想”之意。 devise: 侧重设计的临时性和权宜性,并隐含有更多的设想可用。 conceive: 强调在制定计划之前的先有设想构思。 formulate: 与conceive相反,指在devise之后的具体设计活动。 6.I could in time 我最终能够…… 7.legibly adv.字迹清楚地 例句:He can write as neatly and legibly as the next person if he takes his time over it. 若他不匆匆忙忙写的话,他能写得和别人一样整洁、清楚。 8.help us a little further 帮助我们进一步搞清这个问题 9.With the hand held high in the air, hold the string 这是一个祈使句,谓语动词是hold, with the hand held high in the air是介词短语作方式状语。 10.to and fro 往复,来来回回 11.rotate v. 轮流,(使)旋转 例句:He rotates the handle gently. 他轻轻地转动手柄。 The post of chairman rotates among members of the committee. 主席一职由委员会的成员轮流担任。 【词义辨析】 rotate, revolve, roll, spin, turn, whirl, circle 这些动词均有“转动、旋转”之意。 rotate: 侧重指物体围绕自己的轴或中心旋转,即自转。 revolve: 强调指物体围绕本身以外的中心旋转,即公转。 roll: 指某物在平面上滚动或翻滚。 spin: 指沿内轴迅速而连续旋转,或沿外部一个点作快速圆周运转。 turn: 普通用词,中性,含义广泛,根据搭配,可指作一个圆周运动或连续地作圆周运动,也可指仅是沿圆的弧形转动。 whirl: 指旋转或作圆周运动,侧重急速或力量。 circle: 指作圆周运动。 12.wriggle v.扭动 例句:I can't brush your hair if you keep wriggling all the time. 你要是一直扭来扭去,我就没法给你梳头了。 He had to wriggle his way out. 他得扭著身子才钻了出来。 13.vibration n.颤动;振动;摇动 例句:Even at full speed the ship's engines cause very little vibration. 这条船即使全速前进,发动机的震动也很小。 【参考译文】 地震就像夜间的小偷,不打招呼就来了。因此,有必要发明一种仪器,既不打盹儿,也不睡觉。有些装置非常简单。例如,有一种装置是由一些长短、粗细不同的木棒组成,就像九柱戏的木棒一样坚立着,一旦有地震,就会震动竖立在坚硬的桌上的木棒。如果地震轻微,只有不稳定的木棒倒下;如果地震剧烈,所有的木棒都会例下。由于地震太弱而未惊醒科学家时,木棒倒下的多少和倒下的方向就为科学家记录下了地震的强度和地震方向。 但是,如果要取得真正重大的进展,需要有比这种装置精细得多的仪器。理想的目标是设计出这样一种仪器:当地震发生时,它能用笔在纸上记录下大地和桌子运动情况。我写字时,笔是移动的,纸是静止的。毫无疑问,经过练习,我最终能够学会笔不动而纸动来写字。这听起来似乎是一种愚蠢的想法,但是早期记录地震波的仪器(地震仪)正是采用了这种思路。可是,当桌子、夹笔装置、纸都在移动时,怎么能书写得清楚呢?可以从我们的日常生活观察中找到这个问题的答案。一个站在公共汽车或火车上,当车突然开动时,他为什么会倾倒呢?这是因为他的脚动了,而他的头保持着静止。再做一个简单的实验可以帮助我们进一步理解这个问题。把一个生物拴在一根长绳子的一端,把手高高举在空中握住绳子,让重物几乎接触地面。然后把手前后左右以及旋转摆动,但不要上下摆动。结果会发现,重物是动了,但动得很小,甚至没动。假定把一支笔拴在重物上,笔尖落在地板上的一张纸上,假定地震发生了,地板、纸、你和你的手都会动,重物和笔却不动。由于纸在笔下来回运动,纸的表面就会用墨水记录下地板运动的情况。根据这一原理,制造出了最初的地震仪器,但是纸是卷在慢慢放置的圆筒上的。只要一切都是静止的,笔就会划出一条直线;但是,圆筒受到震动,笔所画出的线就会就会左右摆动。然而,这里所说的仪器记录下来的只是地震波运动中的水平部份,地震波的运动实际比这要复杂得多。假如我们真能看到诸如岩石中一个沙粒子的运动轨迹,那就像一只嗡嗡叫的绿头苍蝇在屋内飞行的轨迹,呈现出上上下下、来来回回、左左右右3种性质的运动。已经设计出了一些仪器,它按照一定的安放方式就可测绘出这三种运动的曲线图。 如果把这种仪器安装在距震中700多英里远的地方,曲线记录就能显示出前后相同的这3种地震波。首先记录下的是纵向波的到达;然后记录下的是横向波的到达,横向波比纵向波传播得慢,在纵向波到过几分钟后能到达。这两种波都是穿过地球而来的。正是从这两种波中的研究中,我们可以了解到地球内部的许多情况。第三种波,即主波,是最慢的,是围绕地球通过表面岩石传来的。
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