1. IN APPARATUS FOR REGULATING THE DENSITY OF A BATH MEDIUM COMPRISING ULTRA-FINE SOLIDS IN WATER, THE COMBINATION INCLUDING A TESTING VESSEL HAVING A FIXED OUTLET ORIFICE AND AN OVERFLOW, A BALANCE BEAM, A HYDROMETER SUSPENDED FROM ONE END OF THE BALANCE BEAM AND HAVING LOCATION IN THE TESTING VESSEL, MEANS CONTINUOUSLY SUPPLYING BATH MEDIUM TO THE TESTING VESSEL TO SUBMERG THE HYDROMETER AND EFFECT MOVEMENT OF THE BALANCE BEAM AS THE DENSITY OF THE BATH MEDIUM MAY VARY, A PAIR OF INDUCTANCE COILS ASSOCIATED WITH THE OTHER END OF THE BALANCE BEAM IN A MANNER CAUSING A BALANCED CONDITION AS REGARDS THE IMPEDANCE OF THE COILS WHEN THE BEAM IS DISPOSED IN A HORIZONTAL NEUTRAL POSITION AND AN UNBALANCED CONDITION WHEN THE BEAM IS ABOVE OR BELOW SAID HORIZONTAL POSITION, A REGULATOR TO WHICH IS SEPARATELY SUPPLIED A DILUTE MEDIUM AND CLARIFIED WATER, A POSITIONABLE DIVERTING GATE WITHIN THE REGULATOR FOR CONTROLLING THE DENSITY OF THE BATH MEDIUM BY CONTROLLING FLOW OF THE DILUTE MEDIUM AND A CLARIFIED WATER, WHEREBY THE LIQUIDS MAY BE DELIVERED TO THE BATH MEDIUM OR DIVERTED FROM THE SYSTEM, SAID GATE HAVING A FIRST OPERATIVE POSITION FOR INCREASING THE DENSITY OF THE BATH MEDIUM BY DIVERTING BOTH LIQUIDS FROM THE SYSTEM, SAID GATE HAVING A SECOND OPERATIVE POSITION FOR DECREASING THE DENSITY OF THE BATH MEDIUM BY DELIVERING BOTH LIQUIDS TO THE BATH MEDIUM, AND SAID GATE IN A NEUTRAL POSITION RETURNING THE DILUTE MEDIUM TO THE BATH MEDIUM BUT DIVERTING THE CLARIFED WATER OUT OF THE SYSTEM, AND AN ELECTRIC POSITIONING MOTOR RESPONSIVE TO THE BALANCE AND UNBALANCED CONDITIONS OF SAID INDUCTANCE COILS FOR ACTUATING THE DIVERTING GATE.