30 HISTORY OF COLCHESTER CORPORATION WATER WORKS. 
was deemed prudent to look for a supplemental supply, as the 
demand was gradually overtaking the yield of the well, as the rest 
level was gradually falling, due to continuous pumping and a 
series of dry years. It is difficult to at once trace the connection 
of a dry year in a well situated as this is, so far away from the 
outcrop of the chalk, and at such a small elevation above sea 
level. The rest level records have, however, since clearly 
shown that as soon as the pumping ceased to be continuous, 
due to the supplemental supply and a series of wet years, the rest 
level speedilv recovered. 
As the present wells could not be touched or deepened under 
any circumstances, an entirely independent source had to be 
found, but there was not much necessity to search far, as the 
Lexden Gravel Springs w r ere close at hand with the water in 
sight. When I was first consulted in 1888, a suggestion was 
then made that the Lexden Springs might be used to supplement 
the then existing supply to the town. The springs w'ere carefully 
gauged, and the whole nest, including the tw T o eastern springs, 
which rise close to the village, were found to yield some 513,000 
gallons per day, but 1887 was a dry year. They were then 
carefully examined by the late Dr. Tidy, a then eminent chemist 
and authority, also by the late Dr. Foster, but as the analysis 
revealed a rather large proportion of nitrates, they suggested 
that a well supply from the chalk would be preferable, hence it 
was that the new' well w T as constructed. At that time a certain 
prejudice existed by a particular school of chemists against so- 
called surface springs containing nitrates, for the reason that the 
method of protecting them against unoxidised manurial matter 
w T as not so fully developed or understood, nor w 7 as so much 
importance then attached to the purifying action of the soil. 
From 1888 until 1902, the matter w'as allowed to sleep, until 
Dr. Thresh was consulted, wffien he was so impressed with their 
importance and the possibility of protecting them, that he re¬ 
ported most, favourably on their adoption. 
The springs are situated on the western boundary of the 
Borough, in the valley of the River Colne, in the Parish of 
Lexden ; they consist of a group of very strong gravel springs, 
which are thrown out to the surface by a junction of extensive 
sand and gravel beds with the London-clay, and are shown on 
Ordnance Map (25 inch scale), sheet xxvii. 7. They unite to 
