It may be carried thousands of miles away to help in building up a coral reef (what that is I must tell you afterwards).

That coral reef may harden into limestone beds.

Those beds may be covered up, pressed, and, it may be, heated, till they crystallise into white marble: and out of it fairer statues be carved, and grander temples built, than the world has ever yet seen.
And if that is not the reason why the chalk is being sent into the sea, then there is another reason, and probably a far better one.

For, as I told you at first, Lady Why's intentions are far wiser and better than our fancies; and she--like Him whom she obeys--is able to do exceeding abundantly, beyond all that we can ask or think.
But you will say now that we have followed the chalk-cart a long way, without coming to the cave.
You are wrong.

We have come to the very mouth of the cave.