xlvi 
PROCEEDINGS OE THE 
existence of some fault or fissure in that direction.” Although we 
may discredit the “ stories of ducks,” the springs at Otterspool 
evidently arise from fissures or channels in the chalk extending in 
this direction, and it seems extremely prohahle that these and other 
swallow-holes in the parishes of Aldenham and Bushey contribute 
materially to the volume of water discharged by the springs. 
When swallow-holes occur in the bed of a stream the water may 
sometimes he seen to disappear entirely in dry seasons, while when 
a large amount of water flows they may take part of it only and 
the stream may flow on merely diminished in volume. In the 
carrier which conveys the water from Elstree Reservoir to the River 
Brent there are some swallow-holes which have to be plugged when 
the water is discharged from the reservoir to prevent the waste of 
the greater part if not the entire volume of water. This carrier 
must be above the plane of permanent saturation of the Chalk, 
but most of our chalk-streams flow at the level of permanent 
saturation. This plane is not horizontal, the rivers flowing at the 
bottom of the valleys being at its lowest point, while on each side 
of the rivers the plane forms an incline towards the higher ground 
of from about 12 to 24 feet to the mile, varying in different years 
and at different times of the year. If in this valley the inclination 
of the surface of the ground did not exceed the inclination of the 
surface of the underground reservoir, the saturated chalk, the water 
would flow over the surface at the same time that it was flowing 
beneath the surface, hut much more rapidly, for there is a resistance 
in the chalk, provided there is no channel or fissure, and it is this 
resistance, the amount of which is determined by the rapidity with 
which the chalk can absorb and part with water, which causes the 
plane of saturation to he inclined from the horizontal. 
Water will always try to find its level, but, in the chalk, although 
always trying to do so, it scarcely ever suceeeds, there being, in 
wet weather at least, a constant accession from above. Thus by 
the accession of water by percolation from above, and the abstraction 
by springs, or wells, or by outlet into rivers below, an equilibrium 
in the plane of saturation is maintained which is represented in 
this neighbourhood by an angle of at least 12 feet to the mile. 
After walking a short distance across the fields the party separated 
at Battler’s Green, some walking to Radlett and others driving to 
Watford. 
Field Meeting, 17 th July, 1884. 
WIDFORD. 
The party assembled at Widford Station at about two o’clock, 
and proceeded first to Widford Church, which has recently been 
thoroughly restored. The paintings in the roof, executed with much 
skill and taste by Miss Gosselin, of Blakesware, were examined 
with great interest; and a fine old gateway in the wall of the 
churchyard, dating probably from the Tudor period, was also 
noticed. It was also found on examination that an old chamber 
