On the Relative Ages of Certain River-valleys in Lincolnshire

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Abstract
In a country which is traversed by a series of escarpments or hill-ranges, the valleys by which its drainage is effected are usually separable into two sets or systems, one parallel to the strike of the ridges, and the other more or lees at right angles to the same. The origin of these longitudinal and transverse valleys, and the process by which escarpments have been intersected by river-valleys, were first explained by Mr. Jukes. He showed also that in the case of a river cutting through a ridge or escarpment, and receiving tributaries from the longitudinal valleys which are parallel to this ridge, the primary or first-formed stream is that opposite to the breach in the escarpment, and that the longitudinal branches, though often of much greater length than this primary stream, are really of secondary or subsequent origin. Stated in general terms, his theory amounts to this, that the original direction of all rivers which cut through ridges was determined by the general slope of the ancient surface over which they began to run, and that when the slope was transverse to the strike of the beds, the channels cut by the earliest rivers necessarily had a similar transverse direction, while the channels in the longitudinal valleys were formed subsequently and concurrently with the development of the ridges or escarpments. A further Corollary to this may, I think, be considered as generally true, viz., that those portions of a river-valley which intersect the same ridge date from the

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