底部的淡水

阶梯的最后一段不一样。岩石不再是干的了。脚下变得更暗、更冷。空气里有湿石头的气味。最下面有一个低矮的洞穴，水面的光在洞顶上晃动。

The last part of the staircase is different. The rock is not dry any more. It gets darker and colder under her feet. There is a smell of wet stone. At the bottom there is a low cave, and light from the water moves across its roof.

就在那里，紧挨着大海，岩石里流出了淡水。波莉尝了尝。水又凉又甜。它本不该出现在这里，可它正是上面这一切的原因。

And there, right next to the sea, fresh water is coming out of the rock. Polly tastes it. It is cold and sweet. It should not be there. And it is the reason for everything above her.

原理是这样的：崖顶的土地是石灰岩。雨水落在石灰岩上不会流走，而是渗进去。水找到小小的裂缝，在石头里面往下走。淡水比海水轻，所以它能一直流到悬崖底部，到了那里还是淡水。

This is how it works. The land on top of the cliff is limestone. Rain does not run off limestone. It sinks into it. The water finds small cracks and travels down inside the stone. Fresh water is lighter than sea water, so it can come all the way down to the bottom of the cliff and still be fresh when it arrives.

现在这道阶梯说得通了。不是士兵，也不是一个晚上。很可能是修士，花了很多年慢慢往下凿，为的是找到这里的水。一座悬崖上的小城可以有高高的城墙和很美的风景，却还是没有水喝。

Now the staircase makes sense. Not soldiers, and not one night. It was probably monks, cutting down slowly for years to reach this water. A town on a cliff can have high walls and a great view and still have nothing to drink.