INLAND WATER SURVEY 419 
cable, there are two contacts and this sheath prevents the instrument giving 
a false reading if water from the strata is falling down the borehole. 
Suitably arranged in a box with the cable drum, are a milliameter and a 
9-volt dry battery. In the case of the single core cable the circuit is 
completed by earthing on to the pump or by a copper bar pushed direct 
into the ground. ‘To obtain the water level the cable is lowered until 
the pointer of the milliameter is deflected, showing contact has been made 
at the water level when the cable is drawn up and the level determined by 
measurement. 
“The pneumatic system consists of a gauge or recorder, mounted usually 
with the pump gauges, together with an air bottle with pressure gauge, 
control cocks, foot pump and copper-piping carried down the borehole 
below the lowest water level. 
The piping (4-in. bore) is clamped to the pump and lowered with it as 
erection proceeds. If the size of the borehole will allow, then a bell is 
usually placed on the end of the pipe to act as a small air reservoir. 
The gauge or recorder is connected direct on to the pipe and a branch on 
the pipe connects to the air bottle, which is turn is connected to the foot 
pump. A control valve is placed directly under the gauge and also on the 
pipe leading from the air bottle. ‘The gauge or recorder is graduated in 
feet below floor level, but the dial is reversed as regards marking when 
compared with a standard gauge. Assume the gauge or recorder was to 
read to a maximum depth of 200 ft. below floor level, then the end of the 
pipe or bell must be exactly this distance below the floor. If the water 
was down to this level there would be no pressure in the pipe and the 
pointer in its zero position would show 200 ft. on the dial or chart. It is 
necessary to maintain a pressure in the air bottle higher than pressure due 
to variations in water level and a gauge is fitted on the air bottles to enable 
the operator to see he is maintaining a suitable pressure with the foot pump. 
If we now assume the water level is 100 ft. below floor level and the 
pressure in the bottle was go lb., then the air admitted to the gauge pipe 
would leak away at the bell or‘pipe end until the pressure just balanced the 
head of water in the borehole and the pointer would now show 100 ft. below 
floor level on the gauge or recorder. Where there are marked variations in 
water level due to alterations in the rate of pumping, or the plant is only 
operating a certain number of hours daily, then the best instrument to instal 
is the seven-day recorder type, as every alteration is indicated and the actual 
time when it occurred, the charts thus obtained giving valuable permanent 
records. 
- A galvanometer is usually provided at each station to check the pneumatic 
depth recorder and also for use in case of a failure on the air-pressure 
system. 
APPENDIX E (c). 
1. PUMPING TESTS AT NEW BORINGS FOR WATER. 
*" 2..GAUGING OVER LONG PERIODS FROM WELLS 
IN THE CHALK. 
By R. C. S. WALTERs. 
1. NEw WATERWORKS, ASHBOURNE, DERBYSHIRE, 1930. 
tthe water is from Bunter beds lying 223-300 ft. below surface, and 
ees Keuper Sandstones and Marls. Borings consisted of a trial bore 
and two permanent boreholes. 
