Method and apparatus for investigating a generally homogeneous medium as to regions of anomalous electrical conductivity

Claim 1

APPARATUS FOR INVESTIGATING A GENERALLY HOMOGENEOUS MEDIUM AS TO REGIONS OF ANOMALOUS ELECTRICAL CONDUCTIVITY, COMPRISING SQUARE-WAVE CURRENT SUPPLY MEANS, INDUCTIVE CIRCUIT MEANS CONNECTED WITH SAID CURRENT SUPPLY MEANS TO BE ENERGIZED THEREFROM AND ADAPTED TO BE COUPLED WITH THE MEDIUM FOR INDUCING ABRUPTLY RISING AND DECAYING PRIMARY MAGNETIC FIELD PULSES IN THE MEDIUM, SAID PRIMARY FIELD PULSES INDUCING SECONDARY FIELD PULSES IN SAID MEDIUM, SAID PRIMARY FIELD PULSES BEING CHOSEN TO HAVE DECAY TIMES SUBSTANTIALLY SHORTER THAN THE DECAY TIMES OF SAID SECONDARY FIELD PULSES, A MAGNETIC FIELD PULSE DECAY TIME MEASURING NETWORK HAVING AN INPUT CIRCUIT COUPLED WITH SAID INDUCTIVE CIRCUIT MEANS AND HAVING INSTRUMENT MEANS FOR MEASURING SUBSTANTIALLY THE DECAY TIMES OF THE SECONDARY FIELD PULSES INDUCED IN THE MEDIUM BY THE PRIMARY FIELD PULSES, SAID NETWORK COMPRISING TIME DELAY PERIODIC SWITCH MEANS RESPONSIVE TO SIGNAL INTENSITY IN SAID NETWORK INPUT CIRCUIT FOR CONTROLLING SAID INSTRUMENT MEANS TO COMMENCE SAID SECONDARY FIELD-PULSE DECAY TIME MEASURING SUBSTANTIALLY UPON TERMINATION OF A PRIMARY PULSE, WHEREBY SAID INSTRUMENT MEANS RESPOND SUBSTANTIALLY ONLY TO THE DECAY TIMES OF SAID SECONDARY FIELD PULSES.