15 
these quarries have been worked to a greater extent 
than in the earlier years that the water does not now 
rise so high in them as formerly was the case, and this 
circumstance must be taken into account, but at the 
same time their capacity for holding water kas been 
increased, 
These quarries, which are located in the upper green 
sand formation, have ceased to be worked as quarries 
and are now devoted to the cultivation of mushrooms. 
Bourne flows are peculiar to the chalk formation and 
are indicative of the large volume of water which at 
times is yielded by this formation. All Bourne flows 
are due to the large amount of rain that falls in the 
higher portions of the district raising the level of the 
ground water which flows down the valleys in a wave- 
like form. 
Underground water is subject to exactly the same 
laws and influences as water flowing over the ground, 
but is slower in its movements, and it has been observed 
in all river areas in which the streams are visible that 
flood waters descend from the highest to the lowest 
parts of the districts, that is, the floods are generated in 
the higher parts of the district, where there is the most 
rain and the least interference with it as regards diminu- 
tion by evaporation and other causes. A Bourne flow 
is nothing more than a flood in the underground water 
passing down from the higher to the lower portions of 
the district swelling out of its ordinary underground 
channels over the surface by reason of the general 
elevation of the underground water line. 
It has often been observed in connection with the 
Croydon Bourne flow that when the flow is small in 
passing down the valley the water enters the ground 
and disappears from sight, as the passages are there 
Godstone 
Quarries 
ceased to be 
worked. 
Bourne flows 
are peculiar 
to the chalk 
formation. 
Due to large 
amount of 
rain falling in 
higher portion 
of district, 
Laws govern- 
ing flow of 
underground : 
water, 
Bourne flow 
is a flood in 
the under- 
ground water, 
In small 
Bournes at 
Croydon 
water dis- 
appears in the 
ground, 
