The eastern Lowlands of England consist of a succession of gently undulating ridges, separated from each other by winding vales or plains. These features have a general trend across the country from south-west or west to north-east or east--a direction determined by the successive outcrops of the different formations. But the denudation of the surface has been so great and so unequal that, despite the continuity and parallelism of the formations, their outcrops have been worn into endless diversities of topographical detail, producing abundant variety among the gentle profiles of the landscapes. As examples of the ridges, we may take the North and South Downs, and the chain of heights that stretches from Wiltshire into Norfolk. The intervening plains may be illustrated by the Weald of Sussex, and by the lower basin of the Thames. The differences between the successive geological formations of the English lowlands never pass a restricted limit in regard to composition and structure. Essentially soft and easily decomposable, the rocks include no thick bands of much harder material than the rest, such as might project in prominent features. The prevailing characteristic of the topography is therefore unbroken placidity. Nowhere does any ruggedness obtrude itself. No part of the ground towers abruptly above or sinks suddenly beneath the general level. The successive ranges of low hills have rounded summits and smooth slopes, which, even when steep, seldom allow naked rock to appear, but conceal it everywhere under a carpet of herbage. So gentle is the inclination of the ground, from the watersheds to the coast, that the drainage winds in sluggish streams that often hardly seem to flow. 'Purling brooks' are scarcely ever to be found. Since the running waters of the country have played no inconsiderable part in the inspiration of our poets, it is well worthy of remark that in the east and south-east of England the streams are, for the most part, silent. We shall see how strongly they are thus contrasted with the brooks that traverse the lowlands of the north.