That is my guess:  and I think it is a good guess, because I have asked Madam How a hundred different questions about it in the last ten years, and she always answered them in the same way, saying, “Water, water, you stupid man.”  But I do not want you merely to depend on what I say.  If you want to understand Madam How, you must ask her questions yourself, and make up your mind yourself like a man, instead of taking things at hearsay or second-hand, like the vulgar.  Mind, by “the vulgar” I do not mean poor people:  I mean ignorant and uneducated people, who do not use their brains rightly, though they may be fine ladies, kings, or popes.  The Bible says, “Prove all things:  hold fast that which is good.”  So do you prove my guess, and if it proves good, hold it fast.

And how can I do that?

First, by direct experiment, as it is called.  In plain English—­go home and make a little Hartford Bridge Flat in the stable-yard; and then ask Mrs. How if she will not make a glen in it like this glen here.  We will go home and try that.  We will make a great flat cake of clay, and put upon it a cap of sand; and then we will rain upon it out of a watering-pot; and see if Mrs. How does not begin soon to make a glen in the side of the heap, just like those on Hartford Bridge Flat.  I believe she will; and certainly, if she does, it will be a fresh proof that my guess is right.  And then we will see whether water will not make glens of a different shape than these, if it run over soils of a different kind.  We will make a Hartford Bridge Flat turned upside down—­a cake of sand with a cap of clay on the top; and we will rain on that out of our watering-pot, and see what sort of glens we make then.  I can guess what they will be like, because I have seen them—­steep overhanging cliffs, with very narrow gullies down them:  but you shall try for yourself, and make up your mind whether you think me right or wrong.  Meanwhile, remember that those gullies too will have been made by water.

And there is another way of “verifying my theory,” as it is called; in plain English, seeing if my guess holds good; that is, to look at other valleys—­not merely the valleys round here, but valleys in clay, in chalk, in limestone, in the hard slate rock such as you saw in Devonshire—­and see whether my guess does not hold good about them too; whether all of them, deep or shallow, broad or narrow, rock or earth, may not have been all hollowed out by running water.  I am sure if you would do this you would find something to amuse you, and something to instruct you, whenever you wish.  I know that I do.  To me the longest railroad journey, instead of being stupid, is like continually turning over the leaves of a wonderful book, or looking at wonderful pictures of old worlds which were made and unmade thousands of years ago.  For I keep looking, not only at the railway cuttings, where the bones of the old worlds are laid bare, but at the surface of the ground; at the plains and downs, banks and knolls, hills and mountains; and continually asking Mrs. How what gave them each its shape:  and I will soon teach you to do the same.  When you do, I tell you fairly her answer will be in almost every case, “Running water.”  Either water running when soft, as it usually is; or water running when it is hard—­in plain words, moving ice.