SHRINKAGE OF THE RIVER LEA. 
237 
its environs, with the exception of occasional pools of stagnant 
water, formed by surface-drainage. 
The principal cause of the drying up of the river in its course 
through Luton has been brought to the notice of the writer 
by Mr. W. R. Phillips, C.E. Towards the close of the nineteenth 
century the local authorities of Luton completed a new drainage 
system of much larger capacity than that which had previously 
existed. Underneath the main sewer, and separated from it by 
an impervious bed of cement, there was also laid down a storm¬ 
water drain of large calibre. The pipes used in its construction 
were placed end to end with open joints, so that any surface- 
springs which were tapped would discharge themselves into it. 
As a natural result of this, there is, at the outflow of the storm- 
drain, just south of Luton, a copious supply of water, whilst the 
river-bed above this point, and for a mile and a half higher, is 
almost dry. Mr. Phillips estimates that under ordinary circum¬ 
stances and in comparatively dry weather there is a daily discharge 
of three-quarters of a million gallons of water, which, after several 
rainy days, is increased to a million and a quarter, an amount equal 
to fhe daily consumption of the township as supplied by the 
waterworks. 
A sample of the water taken at the outflow referred to above 
was submitted to the county analyst, who pronounced it to be good 
drinking water. 
The discharge pipe is situated about a quarter of a mile above 
the Luton Hoo lake, between which points there is at present 
(1902) a continuous flow of clear spring-water. 
The condition of the stream is very different from that which 
would exist if it passed through the town in the open bed of the 
River Lea. It would in that case be subject to constant pollution 
from various causes; but under the existing arrangement the 
stream at its exit, excepting after heavy rains, is so bright and 
clear that the fresh-water Crustacean, Daphnia pulex , finds therein 
a congenial habitat. 
During the progress of the work connected with the excavations, 
the principal cutting for which was nearly parallel with the course 
of the Lea, numerous springs were met with. In some instances 
the inrush of water was so copious and sudden that the men 
employed were compelled to leave their work very hastily. This 
was notably so at the lower end of the town, where the valley is 
narrower than it is farther to the north. The united volume of 
the springs thus interfered with and diverted into the storm-water 
drain accounts for the amount which it discharges. This has been 
continuous up to the present, and there are no indications of 
exhaustion in the near future. 
The prime factor in causing the shrinkage of the sources of the 
Lea is doubtless the diminished rainfall in this district during 
the last twenty years or so. From records published in the 
‘ Transactions ’ of the Hertfordshire Natural History Society it 
appears that the mean rainfall in the upper portion of the valley 
