Abstract: A detector of ferromagnetic materials having a permanent magnet floating in a contaier and restrained under the influence of a soft ferrite mass spaced below it to rotatable movement about a vertical axis centrally of the container. The magnet has a normal at rest position from which it is rotatable when a ferromagnetic material moves through its magnetic field. The magnet carries a curved mirror onto the concaved face of which a light beam is focused, and which beam in an at rest normal position of the magnet is reflected by the mirror onto a zero point of an observer's readout scale. When the magnet is caused to rotate from its at rest position by a ferromagnetic material moving through its magnetic field, the light beam is caused to move away from the zero point; and when the ferromagnetic material has moved out of the magnetic field, the magnet and light beam return to their normal positions but with some oscillation before doing so.

Abstract: A unit comprising a base on which is mounted an atlas of maps each with an arrow thereon indicating the relation of the map area to north, and on which base is also mounted a compass having in a container a liquid on which floats a magnet bearing disk on the surface of which disk is a visible pointer pointing in the direction of the magnet's north pole and the earth's magnetic pole. A ball of non-permanent magnetic material centered on a cover of the container cooperates with the magnet in maintaining the floating disk centered in the container and spaced below the ball. In use, the unit is turnable by the traveler until the arrow on the map points in the same direction as the pointer on the disk, thereby apprising the traveler as to his position relative to his surroundings.