There is, however, yet another effect of colour in our English country towns which, perhaps, you may not all yourselves have noticed, but for which you must take the word of a sketcher. They are not so often merely warm scarlet as they are warm purple;--a more beautiful colour still: and they owe this colour to a mingling with the vermilion of the deep grayish or purple hue of our fine Welsh slates on the more respectable roofs, made more blue still by the colour of intervening atmosphere. If you examine one of these Welsh slates freshly broken, you will find its purple colour clear and vivid; and although never strikingly so after it has been long exposed to weather, it always retains enough of the tint to give rich harmonies of distant purple in opposition to the green of our woods and fields. Whatever brightness or power there is in the hue is entirely owing to the oxide of iron. Without it the slates would either be pale stone colour, or cold gray, or black. Thus far we have only been considering the use and pleasantness of iron in the common earth of clay. But there are three kinds of earth which in mixed mass and prevalent quantity, form the world. Those are, in common language, the earths of clay, of lime, and of flint. Many other elements are mingled with these in sparing quantities; but the great frame and substance of the earth is made of these three, so that wherever you stand on solid ground, in any country of the globe, the thing that is mainly under your feet will be either clay, limestone, or some condition of the earth of flint, mingled with both.