﻿Yol. 64.] SOLTJTION-YALLETS IN THE GLYME AREA. 337 



In some cases a bar runs across the valley, and this bar is 

 occasionally tunnelled by a stone drain to prevent accumulation of 

 water during floods, which leave, after subsidence, a coating of lime- 

 carbonate sediment upon the herbage and thus render it useless. 

 The presence of such a bar would be impossible if the valley were 

 due to erosion. The emergence of water in the valleys is deter- 

 mined by some of the numerous bands of clay in the Great Oolite. 

 If no impervious band crosses the valley, the valley is dry through- 

 out, and the water eventually emerges in the form of soakage, or 

 else in a marked stream frequently beginning (as in a valley near 

 Enstone) in a bubbling spring. 



As these cross-valleys are followed upwards, they gradually 

 become narrower and shallower, and merge as gently into the 

 plateau above as they do into the main valleys below. Whether 

 short or long, they have the same character : they are the same in 

 whatever direction they trend. As they are followed downwards, 

 the change in their character is simply determined by their develop- 

 ment into stream-valleys. The valley-floor along which the stream 

 runs becomes flattened, and the stream gradually meanders over it 

 as the valley widens. But the narrowest stream-valley with a 

 level floor has the same characters as the broad Evenlode. There 

 is a complete gradation. 



On following the Glyme downwards to its junction with the Dorn 

 at Wootton, the valley is seen to widen almost insensibly. The 

 banks retreat continuously farther from the stream, and the level 

 valley-floor becomes gradually broader. The amount of water also 

 increases little by little as more and more cross-valleys are passed. 

 The Glyme at its junction with the Dorn at Wootton meanders 

 over its level floor without any regard to the curving banks of the 

 wide valley that contains it (PL XXXIX, fig. 1). The junction 

 of the two streams is curious. Upon the map the Glyme seems to 

 enter the Dorn Valley, but it simply resumes a direction which it 

 has farther up-stream ; and the Dorn, a younger river apparently, 

 flows into the Glyme at a point up-stream, at right angles and 

 opposite to a bank upon which it has made no impression whatever 

 (see the arrow in fig. 1, PI. XXXIX), as it certainly would have done 

 if the Dorn Yalley had been produced by a body of water suffici- 

 ently strong to erode a channel of this magnitude by overground 

 mechanical action. But the Dorn Valley containing a small and 

 strong stream subsides into the developed Glyme Valley, in the 

 same way as any dry valley enters another, making no more 

 impression at its entrance. The united streams then flow through 

 Blenheim-Park Lake and meander out into the clay-plain to join 

 the Evenlode. The length of the Glyme from its source to Wootton 

 is about 8 miles, and in that distance it falls 400 feet. It rises 

 near Chipping Norton, and simply begins upon a wide plateau 

 beyond which the valley at the base of the triangle first mentioned 

 runs deeply at right angles to it. 



Here, then, is a stream, originating upon a plateau, with no gap 

 at its head, that sinks quietly downwards and in a few miles 



z2 



