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38
ting the water-bearing capacity of a district like that described it
is necessary to know not only the area but the amount of rainfall,
and it must be borne in mind that to be on the safe side it is
necessary to reckon only the percolation which would take place
during a dry year. Through a chalk district water finds its way
to the sea in different ways. Some of the water rises in springs
which break out at the foot of the chalk escarpment; some of it
in wet seasons breaks out in streams in the higher levels, but
during dry periods these streams do not run at all. Some, again,
breaks out in springs in the lower ground. Much water, however,
passes in underground channels; through chalk its passage is
slow. Some of this underground water passes through fissures
and in the lines in which flints occur. It passes also in large
amount through faults in the chalk, which are water-bearing
channels. It may be remarked in passing that a well which
happens to be sunk in the course of one of these faults will afford
a bountiful supply; and headings which are made in connexion
with the deep wells in the chalk are made more or less in the
hope of coming across one of these channels.
The average of the rainfall over the district is estimated to be
about 26 in. It is less than this over the lower ground, and at
Greenwich is about 24 in., but on the higher levels it rises to
30 in. It is a difficult or impossible matter to determine how
much of the rainfall is available for the supply of wells which are
constantly pumped. At one time 6 in. a year of the total rainfall
was supposed to be the amount which it was likely could be used.
Later the estimate was considerably raised, when it was thought
that as much as 12 in. might be available. The present amount
of water used daily by the Kent Company is estimated at about
16,000,000 gallons. According to some evidence that was given
before the last Royal Commission on the Metropolitan Water
Supply it was stated that the Company's Parliamentary area
would be likely to afford a supply of 30,000,000 to 40,000,000
gallons daily.
Present State: General Description.
The whole of the water supplied by the Kent Waterworks
Company is obtained from deep wells and is delivered direct to