But remember, that when you ran through the chalk hills to Reading, you passed from the bottom of the chalk to the top of it, on to the Thames gravels, which lie there on the chalk, and on to the London clay, which lies on the chalk also, with the Thames gravels always over it. So that, you see, the newest layers, the London clay and the gravels, are lower in height than the limestone cliffs at Bristol, and much lower than the old mountain ranges of Devonshire and Wales, though in geological order they are far higher; and there are whole worlds of strata, rocks and clays, one on the other, between the Thames gravels and the Devonshire hills.
But how about our moors? They are newer still, you said, than the London clay, because they lie upon it: and yet they are much higher than we are here at Reading.
Very well said: so they are, two or three hundred feet higher.
But our part of them was left behind, standing up in banks, while the valley of the Thames was being cut out by the sea. Once they spread all over where we stand now, and away behind us beyond Newbury in Berkshire, and away in front of us, all over where London now stands.
How can you tell that?
Because there are little caps--little patches--of them left on the tops of many hills to the north of London; just remnants which the sea, and the Thames, and the rain have not eaten down. Probably they once stretched right out to sea, sloping slowly under the waves, where the mouth of the Thames is now. You know the sand-cliffs at Bournemouth?
Of course.
Then those are of the same age as the Bagshot sands, and lie on the London clay, and slope down off the New Forest into the sea, which eats them up, as you know, year by year and day by day. And here were once perhaps cliffs just like them, where London Bridge now stands.
* * *
There, we are rumbling away home at last, over the dear old heather-moors. How far we have travelled--in our fancy at least--since we began to talk about all these things, upon the foggy November day, and first saw Madam How digging at the sand-banks with her water-spade. How many countries we have talked of; and what wonderful questions we have got answered, which all grew out of the first question, How were the heather-moors made? And yet we have not talked about a hundredth part of the things about which these very heather-moors ought to set us thinking. But so it is, child. Those who wish honestly to learn the laws of Madam How, which we call Nature, by looking honestly at what she does, which we call Fact, have only to begin by looking at the very smallest thing, pin's head or pebble, at their feet, and it may lead them--whither, they cannot tell. To answer any one question, you find you must answer another; and to answer that you must answer a third, and then a fourth; and so on for ever and ever.
For ever and ever?
Of course. If we thought and searched over the Universe--ay, I believe, only over this one little planet called earth--for millions on millions of years, we should not get to the end of our searching. The more we learnt, the more we should find there was left to learn. All things, we should find, are constituted according to a Divine and Wonderful Order, which links each thing to every other thing; so that we cannot fully comprehend any one thing without comprehending all things: and who can do that, save He who made all things? Therefore our true wisdom is never to fancy that we do comprehend: never to make systems and theories of the Universe (as they are called) as if we had stood by and looked on when time and space began to be; but to remember that those who say they understand, show, simply by so saying, that they understand nothing at all; that those who say they see, are sure to be blind; while those who confess that they are blind, are sure some day to see. All we can do is, to keep up the childlike heart, humble and teachable, though we grew as wise as Newton or as Humboldt; and to follow, as good Socrates bids us, Reason whithersoever it leads us, sure that it will never lead us wrong, unless we have darkened it by hasty and conceited fancies of our own, and so have become like those foolish men of old, of whom it was said that the very light within them was darkness. But if we love and reverence and trust Fact and Nature, which are the will, not merely of Madam How, or even of Lady Why, but of Almighty God Himself, then we shall be really loving, and reverencing, and trusting God; and we shall have our reward by discovering continually fresh wonders and fresh benefits to man; and find it as true of science, as it is of this life and of the life to come--that eye hath not seen, nor ear heard, nor hath it entered into the heart of man to conceive, what God has prepared for those who love Him.
Footnotes:
{1} I could not resist the temptation of quoting this splendid generalisation from Dr. Carpenter's Preliminary Report of the Dredging Operations of H.M.S. "Lightening," 1868. He attributes it, generously, to his colleague, Dr. Wyville Thomson. Be it whose it may, it will mark (as will probably the whole Report when completed) a new era in Bio-Geology.