I hear a nightingale warbling in a wood half a mile off; no moving form is visible, no coming step audible; but that perfume increases: I must flee.

我听到夜莺在半英里外的树林里鸣叫；看不到移动的身影，听不到脚步声；但是那香味增加了：我必须逃跑。

Also, in surface water, there is a weak acid, carbonic acid, not sulfuric acid but carbonic acid that helps dissolve the rock. With a little help from this carbonic acid, moving water forms most of the world’s limestone caves.

另外，在地表水中，有一种弱酸，碳酸，有助于溶解岩石的不是硫酸而是碳酸。在这种碳酸的帮助下，流动的水形成了世界上大部分的石灰岩洞穴。