1. IN DRILLING APPARATUS OF THE CHARACTER DESCRIBED HAVING A TUBULAR CASING AND DRILL ROD MEANS INCLUDING A DRILL BIT DISPOSED AT ONE END THEREOF FOR MOVEMENT AXIALLY THROUGH AND BEYOND SAID CASING, THE COMBINATION WHICH COMPRISES GUIDING MEANS DISPOSED IN SAID CASING SUBSTANTIALLY ADJACENT THE END THEREOF NEAREST SAID DRILL BIT FOR COOPERATING SLIDING ENGAGEMENT AT ONE AXIAL POSITION OF SAID DRILL ROD MEANS IN SAID CASING FOR MAINTAINING SAID DRILL ROD MEANS AND SAID DRILL BIT OFFSET THE AXIS OF SAID CASING, SAID GUIDING MEANS FORMING A CONSTRICTION WITHIN