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第1段
1 .<-NARRATOR:-> Listen to part of a lecture in a history class.
请听历史课上的部分内容。
第2段
1 .<-FEMALE PROFESSOR:-> So, most cities of the ancient world tended to be small,
古代的大多数城市往往规模都比较小，
2 .often limited to the banks of a river.
通常都会受到河岸的限制。
3 .They had very little means to expand...
扩张的手段非常少。
4 .these old cities couldn't really cross natural barriers, like rivers,
这些古代的城市无法真正跨越像河流这样的自然屏障，
5 .or be located very far from water sources.
也无法远离水源而立。
6 .But Roman cities, on the other hand, grew much larger.
但是另一方面，罗马城市的规模却发展得很大。
7 .How did this happen?
这是如何做到的呢？
8 .Well, for one thing, the Romans had more advanced technology.
首先，罗马人技术更先进。
9 .Let's look at a couple of Roman developments that allowed their cities to expand.
让我们来看看有助于罗马城市扩张的几项发明吧。
第3段
1 .One development that allowed Roman cities to grow was their advanced building materials.
一项就是他们先进的建筑材料。
2 .The Romans developed a special kind of concrete-
罗马人发明了一种特殊的混凝土，
3 .a building material-that would harden under water,
这种建筑材料在水下会硬化。
4 .and this concrete made new kinds of structures possible.
这种混凝土使得新的建筑类型变为可能。
5 .Take their bridges, for example.
就以他们的桥梁为例吧。
6 .Because of this special concrete, they could build better bridges-
多亏了这种特殊的混凝土，罗马人能够建造出更好的桥梁，
7 .bridges that could go across wide rivers...
这些桥梁能够跨越很宽的河面，
8 .bridges that were big enough to transport equipment and materials, with wagons and carts.
桥面也有足够的空间通行运着设备和材料的车辆。
9 .So with these strong bridges, Roman cities could grow on both sides of the river,
借助着这些坚固的桥梁，罗马的城市可以在河的两岸都进行扩张，
10 .creating larger cities than would have been possible otherwise.
建立原本不可能出现的大城市。
第4段
1 .Another development that helped Roman cities expand was an improved way to move fresh, clean water.
有助于罗马城市扩张的另一项发明就是改良的运送新鲜净水的方法。
2 .People need access to fresh water,
人们需要获取新鲜干净的水源，
3 .and the Romans created an especially effective way to bring it to them-
而罗马人开发出了一种尤其有效的方法把水送到人们面前。
4 .they built structures called aqueducts.
他们建造了一种称为高架渠的物体。
5 .Now, aqueducts are a series of open channels, waterways that stretch from water sources high in the mountains to cities.
高架渠是由一系列户外的渠道组成的，这些水渠从高山上的水源一路延伸至城中。
6 .They were carefully planned and built so that a steady drop in altitude provided a steady flow of water to cities.
这些水渠的安置和建造非常谨慎，所以高处稳定的水源为城市提供了稳定的用水。
7 .These aqueducts could move a tremendous amount of water over great distances,
这些水渠能够远距离地运输大量水源，
8 .and even bring fresh water to places far from rivers.
甚至还能给远离河流的地方带来新鲜的净水。
9 .Because of this, people could have clean water for drinking and bathing, without being located near a river,
多亏了这些水渠，人们才能在不必非得定居在河流附近的情况下，也有可以饮用和洗漱的净水。
10 .so cities were able to grow larger,
因此，城市才能在新的地点
11 .in new locations.
不断扩张。