CIIAI.K WATKK IX IIEKTS. 



watci'-levcl rises too, though to a much less extent. This is what 

 we should naturally expect : hut it is sometimes found that the 

 summit of the watcr-slo])e is not under the summit of the ground- 

 slojie, the wator-hill and the ground-hill being by no means in the 

 same vortical plane ; sometimes, indeed, the water-slope revolts, 

 asserts its independence, and seems not to be governed by the 

 ground- slope. 



A case of this sort in Hertfordshire having come under my 

 notice, I was somewhat troubled thereby, and cast about to find 

 an explanation. Perhaps I have not succeeded, but if I have it 

 does not follow that the explanation Avhich has occurred to me as 

 possible for the Hertfordshire case is to be accepted in all such 

 cases : at different places there may he, and often are, different 

 conditions, and it occiirs to me that a like case, in another 

 county, cannot be explained in the same way as that about to be 

 suggested. 



But, firstly, let us have the facts, for which I rely on the good 

 authority of our County Surveyor. In the course of his official 

 work, Mr. Urban Smith had to undertake some investigations on 

 underground water-levels, for a case in which I had the pleasure 

 of working with him, and he has kindly allowed me to put before 

 you some of the general results ; the details would be out of place 

 here, and, moreover, are not ripe for publication. 



In a section plotted across the valleys of the Rib and the Lea, 

 from north-west to south-east, the following figures came out, and 

 in all cases they refer to feet above Ordnance Datum, or mean 

 sea-level, at the various wells or streams : — 



The gradient of the water is 26 feet in a mile from the first well 

 observed to the llib, and beyond to the next well ; then 9 feet to 

 the next, a little way off; then 29 feet to the next ; 12 to the next, 

 a little way ; and then 11 to below the Lea. 



It will be seen that there is a steady fall in the water-level 

 soiith-eastward, without any rise under the higher ground between 

 the Rib and the Lea, a distance of about a mile and a half. 



A section across the Lea at Ware, from north to south, shows a fall 

 of the water-level from near Thundi'idge to the river, at the rate of 

 30 feet to a mile (150 to 99) ; but the old Ware Waterworks level, 



