288 S. S. BUCKMAN [apkil 



As time goes on the Thames system will suffer most in the west, 

 by the growth of Severn obsequents like the Bristol Avon, Erome, and 

 Chelt, which can give the Cotteswold drainage quicker fall. It may 

 suffer in the south by the growth of the Salisbury Avon. 



The Severn system will suffer in the west by the growth of west 

 Welsh streams ; and the Severn itself may suffer by the shifting of its 

 drainage westward — thus probably the Usk, further developing sub- 

 sequent streams working in the Old Eed Sandstone, will capture the 

 Monnow and the Wye, giving the latter an easier channel than through 

 the gorge of Carboniferous Limestone. 



Conclusion. — To prevent misconception, it may perhaps be desirable 

 to say that " a stream " may be of water or of ice. The latter will 

 follow the drainage lines marked out by the former ; it will not make 

 unaccountable changes of direction. Its chief feature is perhaps to 

 overflow its valley ; and this might greatly aid the headward growth 

 of an attacking rival. 



Many of the statements iu this paper may be termed mere specula- 

 tion, with very few arguments. It is fully admitted. To pursue the 

 matter further, 1 want much better maps than are now to my hand. 

 I require — (1) A clear river-map; (2) a similar river-map with 

 contour lines, and, in figures, the height of all hills and passes ; (3) a 

 similar river-map showing the solid geology, and particularly the dip 

 of the strata ; (4) a similar river-map showing the drift geology. 

 There is of course much to be done in a study of the drift in this 

 connection. That has been shown by J. Prestwich (8), J. W. Gregory 

 (9), and Osborne White (3), not to mention other authorities. There- 

 from can be obtained valuable aid in regard to the chronology of river- 

 valleys and the direction of old streams. 



Thus in the Moreton valley, just on the present divide — at the 

 head- waters of the Evenlode — there is a mass of drift. It shows the 

 Evenlode to have been a big river, that it drained Triassic country, 

 that its waters froze in the north. The ice floated down, bringing 

 Triassic debris, and it melted in passing along the Moreton valley, 

 dropping the debris endwise into a muddy river-bottom. Much of this 

 drift perhaps extended back over Warwickshire, up the original 

 river ; and when the Avon broke into this country, taking off so much 

 of the original river as the depredations of other streams had left — 

 which was little enough — it perhaps attacked this gravel, and has been 

 engaged in transporting it westwards, taking it to Evesham, and 

 perhaps into the Severn valley. And the Stour may have been 

 engaged in retransporting northwards what the original Evenlode had 

 taken the trouble to bring southwards. 1 



The Lower Severn has cut down its valley very much since what 



1 This means that the excavation of the Avon valley, helow ahout a 500 feet contour 

 line, has been accomplished since the deposition of the Moreton drift. What then is the 

 date of that drift ? (later Pliocene, when the climate was getting cold). 



