Thus much for the Thames. As to other pieces of water to be found in public parks, they are mere ponds, and of benefit only locally. As to public fountains, which form the peculiar charm of so many Continental cities, where the melodious splash of water is heard day and night, London possesses none. True, there are two squirts in Trafalgar Square, and the Shaftesbury fountain is making asthmatic efforts to assert itself, whilst the Angel at the top seems to be shooting Folly as it flies all around him in the savoury purlieus of the Haymarket. The small drinking fountains found here and there are evidences of philanthropy, which may be grateful to children and tramps, to horses and dogs, but do not add much to the aquatic features of London. There are canals, it is true, but they are private property, and so fenced, hoarded, and walled in, as to be of no use to the public. And as a rule their water is so dirty that no one with a nose would walk by the side of them, even if allowed to do so. But London was not always so deadly level and so waterless as it is now. In ancient days there were high hills and deep valleys in the very heart of it. From the river Lea to the river Brent on the northern side of London there were numerous rivulets and brooks descending from the northern heights through the City and its western outskirts into the Thames, brooks and rivulets which at times assumed such dimensions as to cause serious inundations. It was the same in the south of London, where from the Ravensbourne to the Wandle similar watercourses reached the Thames from the southern hills. All those brooks between the four rivers we have named, and which alone are still existing, have totally disappeared. What were their features, when they still flowed from northern and southern heights, and what were the causes and the process of their disappearance, we now intend to investigate, by proceeding from east to west, and taking the northern shore of the Thames first.