4 EIVEK-SYSTEM OF WEST HERTS. 



I suggest, therefore, that the Ver was first diverted from its 

 direct course at a very remote period, and captured by a tributary 

 of the Gade, occupying the present valley of the Colne above 

 Watford. The Gade itself then probably flowed through the 

 Oxhey gap, where the North-Western Railway now rims, and 

 was subsequently captured by the Chess, which ran through the 

 Northwood gap along the present course of the Metropolitan 

 Eailway. Finally, the Chess, in its turn, was, I imagine, 

 captured by the Misbourne, a tributary of which worked its 

 way back along the present valley of the Colne below Eickmans- 

 worth, since which time the system has maintained its present 

 course, and the rivers have reached a condition of equililn-ium, 

 though their tributary streams on both sides continue to wear 

 back their head valleys. I would point out that some of the 

 head- waters of the Colne now approach very close to the main 

 stream of the Lea above Hatfield, and are at an elevation btit 

 little aljove the level of that river, so that it is quite within the 

 bounds of possibility that the Colne may capture the upper 

 portion of the Lea also,* if allowed to work out its destiny, 

 though doubtless such a consummation would be prevented by 

 artificial means if it ever threatened seriously to accomplish itself. 



I put forward these suggestions with diffidence, and rather as 

 a suitable subject of investigation than as a verified hypothesis. 

 If the Gade and the Chess ever flowed through the gaps referred 

 to, they would have deposited beds of gravel which should 

 furnish indications of their origin, and I venture to hope that 

 the attention of those of our members who are better qualified 

 than I am to judge of the nature of such deposits, will be 

 directed to the subject, so that the truth or otherwise of the 

 theory I have broached may be established. 



* As the rain which falls on the London Clay area in the hijjher part of the 

 valley of the Colne, flows, through swallow-holes, into the Chalk, which dips 

 south-east towards the valley of the Lea, it almost certainly augments the volume 

 of that river, which is thus, through underground channels, capturing the head of 

 the Colne. — Ed. 



Trans. Hertfordshire Nat. Hist. Soc, Vol. XIII, Part 1, February, 1907. 



