Simultaneous variable density recording system

Claim 1

A METHOD OF PRODUCING A VISUAL VARIABLE DENSITY RECORD OF A PLURALITY OF SEISMIC SIGNALS COMPRISING IMPARTING VIBRATIONS TO THE MEDIUM UNDER INVESTIGATION AT A FIRST LOCATION; DETECTING REFLECTED VIBRATIONS AT A PLURALITY OF SECOND LOCATIONS SPACED FROM SAID FIRST LOACTION AND PRODUCING A PLURALITY OF SEISMIC SIGNALS, EACH BEING REPRESENTATIVE OF THE REFLECTED VIBRATIONS DETECTED AT A RESPECTIVE ON OF SAID PLURALITY OF SECOND LOACTIONS; ESTABLISHING A PLURALITY OF TIMING PULSES; ESTABLISHING A VOLTAGE WHICH INCREASE IN AMPLITUDE IN A STAIR STEP FASHION RESPONSIVE TO THE OCCURRENCE OF ONE OF SAID TIMING PULSES; APPLYING SAID VOLTAGE TO THE Y DEFLECTION INPUT OF AN OSCILLOSCOPE; SEQUENTIALLY SAMPLING EACH OF SAID PLURALITY OF SEISMIC SIGNALS AND APPLYING THE SAMPLED VALUES THUS OB-