Only because the field lies higher than the house; and if--now here is one thing which you and every civilised man should know--if you have water-meadows, or any "irrigated" land, as it is called, above a house, or even on a level with it, it is certain to breed not merely cold and damp, but fever or ague. Our forefathers did not understand this; and they built their houses, as this is built, in the lowest places they could find: sometimes because they wished to be near ponds, from whence they could get fish in Lent; but more often, I think, because they wanted to be sheltered from the wind. They had no glass, as we have, in their windows; or, at least, only latticed casements, which let in the wind and cold; and they shrank from high and exposed, and therefore really healthy, spots. But now that we have good glass, and sash windows, and doors that will shut tight, we can build warm houses where we like. And if you ever have to do with the building of cottages, remember that it is your duty to the people who will live in them, and therefore to the State, to see that they stand high and dry, where no water can drain down into their foundations, and where fog, and the poisonous gases which are given out by rotting vegetables, cannot drain down either. You will learn more about all that when you learn, as every civilised lad should in these days, something about chemistry, and the laws of fluids and gases. But you know already that flowers are cut off by frost in the low grounds sooner than in the high; and that the fog at night always lies along the brooks; and that the sour moor-smell which warns us to shut our windows at sunset, comes down from the hill, and not up from the valley. Now all these things are caused by one and the same law; that cold air is heavier than warm; and, therefore, like so much water, must run down hill. But what about the rainfall?