Now you may see what I meant when I said that the newer rocks, though they lie on the top of the older, were often lower down than they are.
But how do you know that they lie on the limestone?
Look into that corner of the river, as we turn round, and you will see with your own eyes.

There are the sandstones, lying flat on the turned- up edges of another rock.
Yes; I see.

The layers of it are almost upright.
Then that upright rock underneath is part of the great limestone hill above.

So the hill must have been raised out of the sea, ages ago, and eaten back by the waves; and then the sand and pebbles made a beach at its foot, and hardened into stone; and there it is.

And when you get through the limestone hills to Bristol, you will see more of these same red sandstone rocks, spread about at the foot of the limestone-hills, on the other side.
But why is the sandstone two worlds newer than the limestone?
Because between that sandstone and that limestone come hundreds of feet of rock, which carry in them all the coal in England.