Sir Charles Lyell, when he was at Niagara, came to the conclusion
that, taking one year with another, these falls eat back the
cliff at the rate of about one foot a year, as you can easily
imagine they would do, when you think with what force the water
must dash against the bottom of the falls. In this way a deep
cleft has been cut right back from Queenstown for a distance of
seven miles, to the place where the falls are now. This helps us
a little to understand how very slowly and gradually
water cuts its way; for if a foot a year is about the average of
the waste of the rock, it will have taken more than thirty-five
thousand years for that channel of seven miles to be made.

But even this chasm cut by the falls of Niagara is nothing
compared with the canyons of Colarado. Canyon is a Spanish word
for a rocky gorge, and these gorges are indeed so grand, that if
we had not seen in other places what water can do, we should
never have been able to believe that it could have cut out these
gigantic chasms. For more than three hundred miles the River
Colorado, coming down from the Rocky Mountains, has eaten its way
through a country made of granite and hard beds of limestone and
sandstone, and it has cut down straight through these rocks,
leaving walls from half-a-mile to a mile high, standing straight
up from it. The cliffs of the Great Canyon, as it is called,
stretch up for more than a mile above the river which flows in
the gorge below! Fancy yourselves for a moment in a boat on this
river, as shown in Figure 27, and looking up at these gigantic
walls of rock towering above you. Even half-way up them, a man,
if he could get there, would be so small you could not see him
without a telescope; while the opening at the top between the