地球里面

V. M. 希利爾 湯敏

V.M.希利爾（1875—1931），美國著名的兒童教育家、科普作家，創建了卡爾弗特教育體系。他為孩子們編寫了一套趣味盎然的歷史、地理、藝術讀物，即《寫給孩子看的世界歷史》《寫給孩子看的世界地理》《寫給孩子看的藝術史》。本文選自《寫給孩子看的世界地理》。

When I was a very little boy I was very inquisitive. At least， thats what my nurse called me.

One day when I was walking with her along the city pavements， I asked：

“Jane， whats under the pavement？”

“Oh， just dirt，” she replied.

“And what is under the dirt？”

“Oh， more dirt，” she replied.

“Well， whats under that？” I asked. I wasnt satisfied.

“Oh， nothing—I dont know—why are you always so inquisitive？” she asked.

I knew there must be something underneath that， and I just wanted to know what it was—I was just inquisitive.

I had heard that the place bad boys went to when they died was down under the ground somewhere—a big cave， perhaps—and I wanted to know if that was so.

So I made up my mind Id dig down through the World; down， down， down， till I came through on the other side，and then Id know. I was a very little boy， you see. With a tin shovel I started a hole in the back yard behind the grapevines， where no one would know what I was doing. I wanted to keep it a secret until I had dug all the way through. Day after day I worked， digging up first soft ground—that was easy—then I got down to solid ground; that was hard. I had a hole which I could stand in up to my waist.

當我還是一個很小的小男孩的時候，我就是個好奇寶寶。至少，我的保姆是這么叫我的。

有一天，我們沿著城市的人行道散步的時候，我突然問她：“簡，人行道的下面是什么呀？”

她回答我：“噢，只是泥土。”

我接著問：“那泥土下面是什么呢？”

她回答說：“噢，更多的泥土。”

顯然我對這個答案并不滿意，所以我接著問：“可是那下面是什么呢？”

但她只是說：“哦，什么也沒有——我不知道——你為什么總是這么好奇？”

我知道在泥土下面肯定還有什么東西，我想知道那下面到底還有什么——僅僅只是因為好奇。

我以前聽說過，地底下是壞孩子死后會去的地方——也許是一個巨大的洞穴吧。我很想知道這是不是真的。

所以我決定，要挖一條穿過地球的通道去看個究竟。我只要不停地挖呀挖，等挖到地球的另一邊，我就會知道了。要知道，我當時還是個很小的小男孩啊。我拿著一把小鏟子，開始挖這個通道。為了不讓別人知道我在做什么，我選在花園里的葡萄架后面開始。而且我打算在這條通道挖好之前，一直保守這個秘密。一天又一天，我努力地挖著。先挖開的是松軟的泥土——這對我來說倒是非常容易——不久，我就碰到了堅硬的地面。這可就不好玩了。不過我還是挖出一個深深的洞，站在里面可以夠到我的腰了。

Then one evening my father asked， “Whats that hole in the back yard？” My secret was out. He didnt laugh when I told him—at least， out loud—but he asked me if I knew how far Id have to dig.

“Could you dig down as deep as the Washington Monument goes up？” he asked.

I thought perhaps I could， but I was a little doubtful， for the Washington Monument seemed terribly high.

“Men have dug wells many times as deep as the Washington Monument，” my father told me， “but never all the way nor nearly all the way through the World. You would have to dig many thousands of times deeper than the Washington Monument to get down even to the center of the World. Its eight thousand miles straight through the earth and most all the way is rock—just rock， and more rock， thats all.”

Then I gave it up. “How do you know its eight thousand miles if no one has ever been through the World？” asked the inquisitive child. I dont know what my father answered. I was too young to understand. I wonder if you are too young， if I tell you how we know its eight thousand miles; for without ever having been through the World， we do know how far it is.

This is how we know. Its a funny thing， but every ball， whether it is a little ball or a medium-sized ball or a great big ball， is always just a little more than three times as big round as it is through. I have often wondered why this was so—why a ball shouldnt be exactly three times or four times or five times as big round as through， but it isnt. You can try it yourself if you dont believe it. Take an apple or an orange and measure it around and then cut it and measure it through.

一天晚上，爸爸突然問我：“后花園里那個洞是做什么的？” 我的秘密被發現了。當我告訴他我的計劃時，他并沒有笑我——至少沒有笑出聲來——不過，他問我知不知道需要挖多長的通道。

“你能挖出一條像華盛頓紀念碑那樣深的地道嗎？”他問。

我想我也許可以做到。不過我又有一點猶豫，因為華盛頓紀念碑看起來確實是非常非常高。

“人們挖過很深很深的井，比華盛頓紀念碑的高度還要深很多很多倍的井。”爸爸告訴我，“但是這離挖穿地球還是太遠太遠了。即使是要挖到地心，你也需要挖出幾千倍于華盛頓紀念碑的高度那么深才行。因為從這里筆直地到地心，再到地球的另一邊，大約有8000英里，中間你遇到的大部分都是堅硬的巖石——只有巖石，很多很多的巖石——就是這樣。”

于是我放棄了這個計劃。“既然從來都沒有人能穿過地球，你怎么知道從這里筆直地到地心，再到地球的另一邊是8000英里呢？”好奇的孩子追問道。那時候我太小了，不明白爸爸是怎么回答我的。如果我現在告訴你，我們是怎么能不穿過地球就知道它的直徑是8000英里，你能明白嗎？

其實我使用的方法很簡單。有這樣一種非常有趣的現象，世界上的任何一個球——不管是很小的球、中等大小的球，還是超級巨大的球——它表面最大的那個圓圈的長度，都是這個球從頂部到底部的長度的三倍多一點。我一直很奇怪為什么是三倍多一點，而不是剛好三倍或者四倍或者五倍。可是事實就是三倍多一點。你如果不信，可以自己試試。你拿一個蘋果或者橘子出來，先量出它表面最大那個圓圈的長度，然后把它從中間一剖兩半，再量一量它從頂部到底部的距離。你比較一下這兩個長度，就知道我說的沒錯。

Now we know the World is a ball， a huge ball， and yet as it is a ball it must， like all other balls， be a little more than three times as big around as it is through. It is twenty-five thousand miles round the World， because men have actually measured that. So we know that the distance through must be about eight thousand miles， as twenty-five is a little more than three times eight. That is not geography; its arithmetic. If you want to use big words for “around” and “through”， as they do in geographies， you must say “circumference” for “around” and “diameter” for “through”—which mean the same thing： the circumference of the World is twenty-five thousand and the diameter is eight thousand.

The outside of the World is a crust of rock like the skin of a baked potato over the hot inside. Some of the crust that you go through first is in layers， like layers in a jelly-cake， one layer after another， only these rock layers look as if they were made of sand and shells， or coal or little stones， and thats what they are made of. If you could cut the World in half as if it were an apple， it might look something like the picture above. We call it a “Cross Section.”

我們現在已經知道地球是個圓球，雖然這個圓球大得超乎你的想象，但它一定也和其他的球一樣，一周的長度是它從頂部到底部距離的三倍多一點。繞地球一周的距離是25000英里，因為人們確切地測量過。所以我們就很容易知道地球從“頭”到“腳”的距離是8000英里，因為三個8000英里再加一點就是25000英里了。你看，我們已經不是在說地理，而是在做算術了。還有，如果你覺得“地球最大的那個圓圈的長度”和“地球從‘頭到‘腳的距離”這樣的句子很奇怪的話，那么我們就用正規的地理學術語來表述它們。地球最大的那個圓圈的長度叫作周長，地球從“頭”到“腳”的距離叫作直徑。所以，我們也可以說“地球的周長是25000英里，直徑是8000英里”。

地球的表面是一圈厚厚的巖石，就像烤土豆外面那層烤得焦黃的土豆皮。你如果仔細去看，會發現這圈巖石是分層次的。它們一層疊著一層，就像果醬蛋糕里的夾心，只不過巖石的夾心是由沙粒、貝殼、煤塊和各種石塊組成的，就是這些東西組成了地表的巖石圈。如果你能像切蘋果一樣把地球一切兩半，你就能看到地球的內部構造。它的樣子如上圖所示。這種圖，我們叫作縱剖面圖。

Between some of the layers of rock there is coal like jelly in a jelly-cake and in other places there? are gold and silver and diamonds and rubies， and in some of the rock there are pools of oil. Thats why men dig wells down through these layers of rock to get oil， and thats why men dig mines to get coal and gold.

And still farther down the rock is not in layers—it is just solid rock; and still farther down it gets hotter and hotter where the world has not cooled off even yet， until the rock is no longer solid， but melted.

Whenever you see a chimney you know there is a furnace beneath it， and when smoke and fire come out of its top you know there is a fire in the furnace. Well， there are many places on the World where fire and smoke come out of the ground as if through a chimney from a fiery furnace. These places are called volcanoes.

Why was the World made of rock instead of brass or glass or china？ Why is the World shaped like a ball and not like a box， a roller， or an old shoe？

在地球的巖石圈的這些夾層之間，有的地方藏著煤，有的地方則有金、銀，甚至有鉆石和各種寶石，有的地方還富含油田。這就像果醬蛋糕里面夾著的布丁或者水果之類的東西一樣。而人們之所以在巖石中打井、在山里開礦，就是為了找到石油、煤炭、鉆石這些夾在地球這個大蛋糕里面的寶藏。

在這圈分層的巖石下面，就不再分層了，而全是非常非常堅硬的石頭;再往下，地球的溫度變得越來越高，因為地球的核心部分從來沒有冷卻過，連最堅硬的巖石在這里都會被熔化。

如果你看到煙囪，肯定知道下面一定連著個火爐;如果你看到煙囪在冒煙，肯定能猜到爐子里一定有火在燃燒。地球上有很多地方都有火和煙噴發出來，就好像火爐里的火、煙從煙囪里冒出來一樣。地球上這些噴火冒煙的就是火山。

為什么地球是由巖石組成的，而不是銅、玻璃或者陶瓷呢？為什么地球的形狀是個圓球，而不是方盒子、滾筒或者一只舊鞋子的樣子呢？