And if that bottom rock rose up a few miles off, two thousand feet, or any other height, into hills, what would you say then? Would you say: "Oh, but the rock is not bottom rock; is not under the limestone here, but higher than it. So perhaps in this part it has made a shift, and the highlands are younger than the lowlands; for see, they rise so much higher?" Would not that be as wise as to say that the bottom of the pond was not there before the pond mud, because the banks round the pond rose higher than the mud? Now for the soil of the field. If we can understand a little about it, what it is made of, and how it got there, we shall perhaps be on the right road toward understanding what all England--and, indeed, the crust of this whole planet--is made of; and how its rocks and soils got there. But we shall best understand how the soil in the field was made, by reasoning, as I have said, from the known to the unknown. What do I mean? This: On the uplands are fields in which the soil is already made. You do not know how? Then look for a field in which the soil is still being made. There are plenty in every lowland. Learn how it is being made there; apply the knowledge which you learn from them to the upland fields which are already made. If there is, as there usually is, a river-meadow, or still better, an aestuary, near your town, you have every advantage for seeing soil made. Thousands of square feet of fresh-made soil spread between your town and the sea; thousands more are in process of being made. You will see now why I have begun with the soil in the field; because it is the uppermost, and therefore latest, of all the layers; and also for this reason, that, if Sir Charles Lyell's theory be true--as it is--then the soils and rocks below the soil of the field may have been made in the very same way in which the soil of the field is made. If so, it is well worth our while to examine it. You all know from whence the soil comes which has filled up, in the course of ages, the great aestuaries below London, Stirling, Chester, or Cambridge. It is river mud and sand. The river, helped by tributary brooks right and left, has brought down from the inland that enormous mass. You know that. You know that every flood and freshet brings a fresh load, either of fine mud or of fine sand, or possibly some of it peaty matter out of distant hills. Here is one indisputable fact from which to start. Let us look for another. How does the mud get into the river? The rain carries it thither.