So sailing ships, in old times, fastened themselves to those rings, and rode against the stream till the tide turned, and carried them up to Bristol.
But what is the tide?
And why does it go up and down?
And why does it alter with the moon, as I heard you all saying so often in Ireland?
That is a long story, which I must tell you something about some other time.

Now I want you to look at something else: and that is, the rocks themselves, in which the rings are.

They are very curious in my eyes, and very valuable; for they taught me a lesson in geology when I was quite a boy: and I want them to teach it to you now.
What is there curious in them?
This.

You will soon see for yourself, even from the steamer's deck, that they are not the same rock as the high limestone hills above.

They are made up of red sand and pebbles; and they are a whole world younger, indeed some say two worlds younger, than the limestone hills above, and lie upon the top of the limestone.