2 MR. B. M. GRIFFITHS ON THE 
drains to the Thames. The overflow streams are of small volume, and their 
courses are for the most part through drainage ditches. The soil is London 
Clay. 
Description of the Pools :— 
1. Bulmershe North Pool. 
Area about seventeen acres. Depth about ten or twelve feet over the 
larger area. Banks covered with tall trees and a thick undergrowth 
of Rhododendron, A small stream enters at the top end. Sides of 
the pool fringed with large masses of Equisetum limosum and some 
Nymphea alba ; on the bottom much Myriophyllum, and in some 
places Polygonum amphibium, Water dark in colour and opaque, 
owing to quantity of plankton. Middle of pool free from weeds. 
Temperature of water six inches below the surface, 18 deg. C. 
2. Bulmershe South Pool. 
Area about twenty-three acres. Pool much broader than the 
former and not so much shaded by trees. Banks covered with thick 
growth of Rhododendron, with trees some distance behind. At the 
upper end is park-land extending back to the mansion. Depth of 
water about six to ten feet over the larger area but shallower towards 
top end, where considerable masses of Polygonum amphibium and 
Ranunculus aquatilis occur. Water clear. At the south-west angle 
there is a small sphagnum bog. Temperature, 18 deg. C. 
3. Whiteknights Pool. 
Area about eighteen acres. Pool elongated. Banks of pool lined 
with tall but not densely crowded trees; the dam lined with pollard 
willows. Sides of pool fringed with broad sheets of Nymphea alba ; 
middle completely free from weeds. Depth about twenty feet or 
more in middle, and the sides rapidly shelving. Water brownish in 
colour and opaque, owing to quantity of plankton. Temperature, 
20 deg C. 
The water-supply of all the pools is from bottom springs and from park- 
land, and it is probably entirely free from contamination either from arable 
land or from house-drainage. In no case does a strong stream enter, and 
the outflows are small. The two Bulmershe Pools are separated by only a 
few hundred yards of woodland. Whiteknights Pool lies about a mile west 
of Bulmershe South Pool. 
The vollections of plankton were taken by means of a fine silk net, six 
inches in diameter and eighteen inches long, towed behind a boat at a depth 
of a few inches below the surface. The course of the boat was along the 
middle of the pool, where weeds were absent. 
