*7 



tributary, F, of E. F and B are in antagonism. There is doubtless 

 some subsidiary watershed, caused by some more durable beds of 

 s, s, between their springs. We must now search for some factor 

 which will give either F or B the mastery, and it may be looked for 

 either on the courses of those streams or the main rivers which they 

 feed. It may be that F or E on the one hand, or B or A on the other, 

 have found a more yielding bed, one which they can more quickly 

 deepen, to give their head water more fall, or perhaps the course of 

 one or the other combination finds a readier access to the sea, which 

 would give the same effect. 



The latter state of things is shown in the figures. On the left 

 the immediate junction of E will be observed. Other things being 

 equal, E and all its affluents will lower their valleys and enlarge 

 their dominions with enhanced powers relatively to the A system. 

 The result is that F will capture the head waters of B, and the latter 

 will, probably in a series of steps with stagnant poises, be eventually 

 reversed and joined to F and will partake in its accelerated activity. 

 In course of time fig. i will become as fig. 2. Here the position of 

 the various rivers has not been altered, though in nature some 

 lateral shifting would usually take place. Also the escarpment of 

 h, h is not shown to have receded, to enable a readier comparison of 

 the two figures. Only the little " corrie " formed by D is somewhat 

 enlarged and deepened. But the entire water system of the plain 

 s, s is altered. The capture of B by F is obviously followed by that 

 of the head waters of A, now A 1, and of the affluents C and D. B 

 is now an obsequent, and so also is the small intermediate portion of 

 A, now A 2, which is seen reversed and adding its quota to the 

 waters of E. A itself, the much reduced A 3, now has its rise some- 

 where within the gorge, out of sight in the diagram. The lower 

 valley of A 3 would be found in nature to be what Professor Davis 

 has called a "misfit," many sizes too large for its stream, whose 

 meanderings would bear no relation to the curves of its valley sides. 



A very perfect instance of an A 3 is found in the Blackwater 

 which now rises at Aldershot and flows north-westward into the 

 Loddon. The South Western Railway crosses it a short distance 



on the London side of Farnborough station. An examination of the 

 remarkable dry gap in the chalk range between the rise of the 

 Blackwater on the north and the abrupt angle in the course of the 

 Wey on the south will lead to the conclusion that the Wey has been 

 purloined from the Thames at this point, and its lower valley, of 



Fig. 2. A later stage of Fig. 1, 



