Seismic depth gauging system

Claim 1

IN A FLUID PRESSURE INDICATOR, A MAGNETIC YOKE COMPRISING COAXIAL INNER AND OUTER CYLINDERS SEPARATED BY AN ANNULAR GAP THEREBETWEEN, A MAGNETIC MATERIAL ELEMENT PERMANENTLY CLOSING SAID GAP AT ONE END OF THE YOKE, A MANDREL PASSING THROUGH THE INNER CYLINDER AND MOVABLE ALONG THE AXIS THEREOF, AN ARMATURE CARRIED BY THE MANDREL, SAID ARMATURE BEING ADAPTED TO CONTACT THE FACES OF SAID CYLINDRICAL MEMBERS PERPENDICULAR TO THE AXIS THEREOF TO CLOSE MAGNETICALLY SAID ANNULAR GAP AT THE OTHER END OF THE YOKE, MEANS COMPRISING A DIAPHRAGM EXPOSED TO FLUID PRESSURE FOR APPLYING PRESSURE TO THE MANDREL IN SUCH A DIRECTIN AS TO MOVE THE ARMATURE OUT OF CONTACT WITH SAID YOKE, A SOLENOID WINDING DISPOSED IN SAID ANNULAR GAP, MEANS COMPRISING A SOURCE OF CURRENT CONNECTED IN CIRCUIT WITH THE SOLENOID WINDING FOR APPLYING TO THE ARMATURE AN ELECTROMAGNETIC PULL TO MOVE SAID ARMATURE IN THE OPPOSITE DIRECTION WHEN SAID CIRCUIT IS CLOSED, CURRENT CARRYING MEANS MANUALLY OPERABLE TO CHANGE THE INTENSITY OF THE CURRENT IN THE SOLENOID TO CAUSE THE SOLENOID TO PULL THE ARMATURE INTO CONTACT WITH THE FACES OF SAID CYLINDRICAL MEMBERS, SIGNALS MEANS RESPONSIVE TO THE ELECTRICAL TRANSIENT ARISING WHEN SAID FACES ARE CONTACTED BY SAID ARMATURE, AND INDICATOR MEANS CONNECTED IN SAID CIRCUIT FOR INDICATING THE INTENSITY OF THE CURRENT IN THE SOLENOID WINDING AT THE INSTANT WHEN SAID ANNULAR GAP IS MAGNETICALLY CLOSED BY SAID ARMATURE AGAINST THE EFFECT OF SAID PRESSURE.