the particles prior to entry into the transition throat 70 a piston port bypass 91 may be additionally provided on the actuator 90 to permit selective bleeding of the pressure within the actuator 90 during the mining operation as by introduction of ball plugs into the peripheral portion of the bore hole from ground surface as shown in fig2 the mining section 10 additionally includes a supplemental liquid supply conduit 106 which extends from the lower end of the jet pump supply conduit 22 terminating adjacent the lower end of the casing 30 the supplemental liquid supply conduit 106 is utilized to transport a small quantity of liquid into the lower end of the casing 30 such that mined tar sands entering through the bottom inlet 55 is supplied with a sufficient quantity of liquid to assume a slurry condition the supplemental liquid supply conduit 106 is preferably provided with a conventional restrictor 108 which reduces the pressure and velocity of liquid passing through the supplemental supply conduit 106 so that the jet pump action generated by the jet pump nozzle 42 and eductor venturi 46 is not disturbed during operation advantageously the conduit 106 may be formed having one or more discharge outlets 107 which direct the supplemental liquid.