Abstract: A directing instrument for control of the inclination of the drill post of a drilling apparatus comprising means for sensing the inclination of the post in two directions at right angles to one another. Said means being supported by a holder arranged to be mounted rotatably on said post and so that the axis of rotation of said holder can be set relative to the post dependent on the type of operation to be carried out.

Abstract: A vibrating device comprising a cylinder with at least one inlet opening for a pressure fluid and at least one outlet opening and a piston moveable in the cylinder. The cylinder is arranged to serve as a vibration generator and to be mechanically connected to the object which is to be subjected to vibrations. The piston moveable in the cylinder is made with a relatively great weight and is arranged to be moved from an inner end position to an outer end position by the pressure fluid admitted via the said inlet opening and to return to the said inner position under the influence of its own weight and escape of the said pressure fluid through the outlet opening.