You open your young eyes. And I do not blame you. I looked at this very
glen for fifteen years before I made that guess; and I have looked at it
some ten years since, to make sure that my guess held good. For man
after all is very blind, my dear boy, and very stupid, and cannot see
what lies under his own feet all day long; and if Lady Why, and He whom
Lady Why obeys, were not very patient and gentle with mankind, they would
have perished off the face of the earth long ago, simply from their own
stupidity. I, at least, was very stupid in this case, for I had my head
full of earthquakes, and convulsions of nature, and all sorts of
prodigies which never happened to this glen; and so, while I was trying
to find what was not there, I of course found nothing. But when I put
them all out of my head, and began to look for what was there, I found it
at once; and lo and behold! I had seen it a thousand times before, and
yet never learnt anything from it, like a stupid man as I was; though
what I learnt you may learn as easily as I did.

And what did I find?

The pond at the bottom of the glen.

You know that pond, of course? You don't need to go there? Very well.
Then if you do, do not you know also that the pond is always filling up
with sand and mud; and that though we clean it out every three or four
years, it always fills again? Now where does that sand and mud come
from?

Down that stream, of course, which runs out of this bog. You see it
coming down every time there is a flood, and the stream fouls.

Very well. Then, said Madam How to me, as soon as I recollected that,