The long and strong backbone of the North Downs extends, roughly speaking, from Kent, by way of Dorking and Guildford, to the source of the Avon, north of Salisbury Plain; and the South Downs run parallel, more or less, through Sussex and Hants to the Dorset heights. From these green hills spring the streams which will be briefly traced from source to sea in this chapter. They are not rivers of first account in their aid to commerce; even the pair which combine in the formation of Southampton Water have never been reckoned in the nomenclature of dock or port. To the angler, however, some of these chalk streams are exceedingly precious--as they indeed ought to be, when a rental varying from fifty to a hundred pounds per mile per annum is gladly paid (and taken) for the right of fishing with rod and line. Such choice preserves are stocked with trout of aristocratic quality, trout which can only be reared in streams issuing from the chalk; their water, when unpolluted by contact with towns, is crystal clear; and the beds of gravel and fine sand favour the growth of typical vegetation, which in its turn favours typical water insects and other food suitable for the highest class of non-migratory salmonidæ. Wholly different from such noisy, turbulent, masterful rivers as those which distinguish North Britain, these chalk streams enter into the very spirit of that sweet pastoral scenery which suggests repose, peace, and plenty. They maintain for the most part an even course, tranquilly flowing without fret or violence through level land, and pursuing their tireless journey seawards, unobstructed by the rugged rocks, obstinate boulders, and uneven beds which provoke your mountain-or moorland-born waters into thunderous roar, angry swirl, and headlong rapidity. For foam-flecked pools, and mighty leaps in romantic gorges, the South-country chalk stream offers forget-me-nots by the margin, and beds of flowers blossoming from its harmless depths. It is with rivers of this class we have now to deal, presenting such features as may be noticed within the limits which have been assigned to the present chapter. [Illustration: RIVERS OF KENT AND SUSSEX.]