1. A CARRIAGE SUPPORTING ASSEMBLY COMPRISING A PLURALITY OF TRACKS ARRANGED IN A COMMON PLANE AND INTERSECTING ONE ANOTHER, AND AT LEAST ONE CARRIAGE INCLUDING SUPPORTING WHEELS SUPPORTED ON SAID TRACKS, SAID WHEELS HAVING AXES OF ROTATION WHICH ARE PERPENDICULAR TO SAID PLANE AND STATIONARY RELATIVE TO SAID CARRIAGE, EACH SAID TRACK COMPRISING AT LEAST TWO PARALLEL RAILS IN SPACED RELATION, EACH OF WHICH RAILS INCLUDE A SUPPORTING SURFACE FOR SUPPORTING SAID WHEELS, SAID SUPPORTING SURFACES OF AT LEAST ONE OF SAID PARALLEL RAILS BEING INTERRUPTED AT THE INTERSECTION OF SAID TRACKS TO FORM A PASSAGE THEREAT TO PERMIT THE WHEELS OF SAID CARRIAGE TO BE TRANSFERRED FROM SAID