In speaking of the course of the Tamar, I should wish to make a distinction betwixt the channel and the bed of the river, if I may be allowed so to use these two words. By the channel, I mean the whole flat surface over which a river spreads its waters during the floods of winter, extending to the foot of the hills which form the valley. By the bed, I mean the narrow channel to which the water is confined during that "belle saison," when all Nature presents her beauties to advantage; when all rivers sleep in their beds, and even the most turbulent are restrained within their narrowed limits. Let us now consider the process of Nature in forming this bed. Light never moves but in straight lines. Water always takes some degree of curvature. The rays of light may be broken by reflection, or refraction, but can never be bent. Water, on the contrary, may easily be bent, but cannot be broken without changing its fluid character to froth. The course of a river is never straight, and seldom along the middle, or lowest part of the flat, but it shoots across, from side to side, increasing its utility by thus retarding its progress: this observation applies to all rivers, though I was first led to examine the subject by the tortuous course of the river Manyfold, in Derbyshire.