1. A HYDRAULIC CONTROL SYSTEM FOR EFFECTING ROTARY MOVEMENT OF A SHAFT ON EACH SIDE OF A NEUTRAL POSITION COMPRISING HYDRAULIC ACTUATING MEANS OPERATIVELY CONNECTED TO SAID SHAFT TO ROTATE THE LATTER, SAID ACTUATING MEANS HAVING CONTROL PORTS, A VALVE ASSEMBLY HAVING FLUID PRESSURE INLET AND RETURN PORTS, A SOURCE OF FLUID UNDER PRESSURE CONNECTED TO THE PRESSURE PORTS OF SAID VALVE ASSEMBLY, A RESERVOIR CONNECTED TO SAID RETURN PORTS, SAID VALVE ASSEMBLY HAVING MOVABLE VALVE MEANS, RESILIENT MEANS REACTING AGAINST SAID VALVE MEANS, NORMALLY RETAINING THE LATTER IN NEUTRAL POSITION TO BLOCK FLOW OF FLUID TO SAID ACTUATING MEANS, A MANUALLY OPERABLE FLUID PRESSURE SOURCE OPERABLY CONNECTED TO SAID VALVE ASSEMBLY TO EFFECT MOVEMENT OF THE VALVE MEANS THEREOF TO CONNECT SAID SOURCE OF FLUID UNDER PRESSURE TO SAID HYDRAULIC ACTUATING MEANS, AN ELECTRICALLY OPERABLE CONTROL MEANS OPERABLY CONNECTED TO SAID VALVE ASSEMBLY TO EFFECT SUCH MOVEMENT OF THE VALVE MEANS, AND MEANS TO SHORT CIRCUIT SAID MANUALLY OPERABLE FLUID PRESSURE SOURCE WHEN SAID ELECTRICALLY OPERABLE CONTROL MEANS IS ACTUATED.