Croydon 
drainage area 
and how 
discharged. 
Author has 
kept records 
of water dis- 
charged from 
Oxted Tunnel 
since 1881. 
Investigations 
of amount of 
water yielded 
by chalk, 
Rainfall 
Scations 
established. 
16 
large enough for its conveyance without appearing at 
the surface. The largest surface flow of the Bourne 
always occurs immediately below the ‘‘ Rose and 
Crown”? at Coulsdon, from which point down the 
valley it diminishes. 
The Croydon drainage area, which supplies the 
Bourne and the underground waters to the Croydon 
branch of the River Wandle, contains an area of 24 
square miles. Of this area in ordinary times 14 square 
miles should discharge their waters from Purley Junc- 
tion down the Brighton Road Valley directly into the 
head of the Wandle at Croydon, while 8 square miles 
drain unde the intervening high grounds and dis- 
charge into Waddon Mill Pond; the waters of the 
remaining 2 square miles have been diverted by the 
Oxted Railway Tunnel. In times of the Bourne flow a 
large proportion of the flow passes in the direction of 
Croydon and a lesser volume flows to Waddon ; at all 
other times, unless interfered with by pumping, the 
yield of the respective areas is identical. 
The Author has kept continuous records of the 
waters discharged from the Oxted Tunnel since the 
year 1881, and he also knows exactly the quantity of 
water that has been discharged both from the Croydon 
area and the Waddon area for many years past, the 
records of which are kept up to date. 
In making an investigation of the amount of water 
that is yielded by the chalk formation on this particular 
Croydon area, the Author found it necessary to establish 
as many rainfall stations as could be secured, and 
wherever he could get observers he established a rain- 
fall station, which were continued for a considerable 
period, and in this way more than twenty rainfall 
stations were established in the district and its imme- 
