With a view to this, it has become increasingly common of late years to publish not the voltages actually observed, but values deduced from them for the potential gradient in the open in volts per metre.
The potentials that have to be dealt with are often hundreds and sometimes thousands of volts, and insulation troubles are more serious than is generally appreciated.
Liideling (9) found for the mean value for 1904 in volts per metre 242.
At Such Times Gradients Of 400 Or 500 Volts Per Metre Are By No Means Unusual At Kew, And Voltages Of 700 Or Boo Are Occasionally Met With.
The charge on the earth itself has its surface density given by v = - (I/47r) X125 volts per metre, =0.000331 in electrostatic units.