by MAURICE BURTON from Curiosities of animal life
7-1. Not all sounds made by animals serve as language, and we have only to turn to that extraordinary discovery of echo-location in bats to see a case in which the voice plays a strictly utilitarian role.
譯文動物發出的聲音並不都起語言作用。我們只需舉發現蝙蝠的回聲定位這個不同尋常的例子，就能知道聲音起著極其實用的作用。
講解Not all sounds…這裏否定的是其中壹部分，叫部分否定句。all，every，both，always等用於否定結構時不是全部被否定，而是表示其中的壹部分被否定。而且英語多半將not置於謂語中。
例如： All is not a gold that glitters.（即Not all that glitters is gold.） 閃閃發光物，未必盡黃金。
Every one cannot write novels.（即Not every one can write novels.） 不是所有的人都能寫小說。
I don’t like both of the novels.（即I like only one of the two novels.） 這兩本小說我不是都喜歡。
plays a strictly utilitarian role直譯為“扮演絕對實用的角色”，可譯為“發揮絕對實用的作用”。
單詞和短語
turn to：求助於；求教於；查閱（to try to get help, advice, or sympathy from sb.），
例如： You can always turn to me for help. 妳隨時可以來找我幫忙。
utilitarian：實用的（intended to be useful and practical rather than attractive or comfortable），
例如： A good cloth coat is more utilitarian than a fur one. 壹件優質的布外衣要比壹件毛皮外衣更有用。
另掌握utilitarianism（功利主義）壹詞。
7-2. To get a full appreciation of what this means we must turn first to some recent human inventions.
譯文要透徹理解這句話的含義，我們應先回顧人類最近的幾項發明。
講解to get a full appreciation of what this means作目的狀語，修飾turn。不定式作狀語放在句首，比放在後邊更要正式，語氣較重。what this means是名詞性從句，作of的賓語。this指上句we have only to turn…plays a strictly utilitarian role。
單詞和短語
appreciation：估價；評價；鑒別（an understanding of the importance or meaning of sth），
例如： They are mistaken in their appreciation of the country’s economic conditions. 他們對國家經濟形勢的判斷是錯誤的。
have a keen appreciation of a joke 能深刻領會壹句笑話的妙處
appreciation的動詞形式為appreciate，形容詞形式為appreciative。
7-3. Everyone knows that if he shouts in the vicinity of a wall or a mountainside, an echo will come back.
譯文大家都知道，如果有人在墻壁或半山腰附近發出喊聲，他就會聽到回聲。
單詞和短語
in the vicinity (of sth.)：（在……）附近；（與……）接近（in the area around a particular place），
例如： a mansion in the vicinity of the lake 湖濱大廈
His income is in the vicinity of $50,000 他每年的收入將近五萬美元
7-4. The further off this solid obstruction, the longer time will elapse for the return of the echo.
譯文固體障礙物越遠，回聲返回所用時間就越長。
講解obstruction後省略了is。for the return of the echo作time的定語。
單詞和短語
obstruction：阻塞物；障礙（物）（when sth blocks a road, passage, tube etc, or the thing that blocks it），obstruction的動詞形式為obstruct。
elapse：（時間）消逝，過去（if a particular period of time elapses, it passes），
例如： Five years elapsed before he returned. 過了5年他才回來。
7-5. A sound made by tapping on the hull of a ship will be reflected from the sea bottom, and by measuring the time interval between the taps and the receipt of the echoes, the depth of the sea at that point can be calculated.
譯文敲打船體所發出的聲音會從海底反射回來，測出回聲與原聲間隔的時間就可算出該處海洋的深度。
單詞和短語
receipt:收到，接到（when sb. receives sth.），
例如： We are awaiting the receipt of further information. 我們正在等著接獲進壹步的信息。
receipt另壹常見意為“收據，發票”，receipt的動詞形式為receive。
interval：（空間、時間上的）間隔；間距；間隙；空隙（the period of time between two events, activities, etc），
例如： an interval of 30 years 30年的間隔
the interval between a lightening flash and the following thunder 電閃與隨後雷鳴之間的間歇
an interval of 10 metres between posts 柱間10米的距離
She has intervals of freedom from worry. 她間或也有擺脫煩惱之時。