152 
J. HOPKINSON-WATER AND WATER-SUPPLY 
probably more rapid now than at any former period, owing to the 
natural depression being augmented by artificial means. All our 
dry chalk valleys have been formed originally by running streams. 
In some the plane of saturation is still so near the surface that 
water is seen in them after exceptionally wet periods. Others, 
now always dry, appear to have had water flowing down them 
within historic times. The valley immediately to the west of St. 
Albans is one of these. The Yer has considerably declined in 
volume within the memory of the present generation, and as far 
back as the thirteenth century it was known to have been a larger 
river than it was then, for Matthew Paris states that “the Werlam 
river,” as it was called in his time , 11 was once very large , and flowed 
about the city [of Yerulam].” 
The River Colne, above its junction with the Yer, is now a 
smaller stream than the Ver, although its catchment-basin to that 
point is larger than that of the Yer. This diminution in its volume 
is doubtless chiefly due to the whole of the water draining a con¬ 
siderable area above North Mimms being now usually absorbed in 
swallow-holes in the Chalk at Potterells. The channels through 
which water is being conveyed away from these swallow-holes must 
be gradually enlarging, but they owe their existence to the lowering 
of the plane of saturation in the Chalk ; or they may even formerly 
have conveyed water into the river. It is but rarely now that 
the plane of saturation is so raised that the water flows on through 
North Mimms Park past the mansion which from its situation seems 
undoubtedly to have been built to look upon a flowing river, the 
bed of which is now dry during the greater part of every year, and 
in some years all the year through. 
At one time the whole valley of the Lea in the parish of Wheat- 
hampstead, Cussans states in his ‘ History of Hertfordshire,’ * 
“was one vast lake or mere,” fordable at certain places, “as at 
Ratford, Pickford, and Mereford, now called Marford. At its 
narrowest part ... it was spanned by a bridge, over which passed, 
and still passes, the road from St. Albans to the North.” It con¬ 
tained two islands, and “terminated at Water End, in the adjoining 
parish of Sandridge.” He also refers f to a sketch in Chauncy of 
Littlecourt, between Corneybury and Euntingford, showing the 
River Rib, which flows before the house. It is represented, he 
says, “as being nearly on a level with the banks, and three figures 
appear fishing in the stream.” Now “ the bed of the river is quite 
dry for the greater part of the year,” and fishing is out of the 
question, though “ forty [now nearly sixty] years ago the river 
contained an abundance of pike, roach, perch, and trout.” There 
are vestiges and records of several water-mills on this river, for 
which the supply of water is now utterly inadequate. 
To come to more recent times, it may be stated that for the last 
ten or twenty years or longer, the water-power in our rivers, both 
the Colne and the Lea and their tributaries, has been declining, so 
* “ Hundred of Dacorum,” p. 326. 
f “ Hundred of Edwinstree,” p. 83. 
