At altitude you see it all at once. You see Lake Ontario on one side and Lake Erie on the other,and linking them the 34-mile Niagara River. Then, coming down lower, you see the falls themselves, along a front almost a mile wide, plunges[急降] over a 182-foot cliff and flows off through a deep, narrow gorge[峡谷].
And right away, with a flash of understanding, you see the main fact about the Niagara Falls. The falls are moving,the seven-mile-long gorge is merely the track the falls have made as they move along. This instantly reverses all your ideas. On the ground it seemed that the water fell because there was this low place for it to fall into the gorge. Now you see it is the other way round. The falls are the cause, and the gorge is the result. Niagara Gorge looks like the track eaten into an apple by a worm[虫].
Niagara differs from the waterfalls you find in mountains, where a thin stream of water comes down a mountainside, half-flying. Some of them are much higher than Niagara,and perhaps more beautiful,but they lack mass and cutting power[爆发力]. Niagara belongs to the heavyweights - where a whole solid river plunges bodily over a cliff. The real sight from above is the gigantic[巨大的] movement of the falls themselves,digging the gorge.