A magnetic apparatus (10) is provided having a bottom plate (12), a top plate (14), a first magnet guide (16), a second magnet guide (18) and a magnet member (20) which is slidable upon a slide axis (22) through apertures (40) and (54) of first magnet guide (16) and second magnet guide (18) respectively. The magnetic apparatus (10) is shown in a closed position in FIG. 1 for use in conjunction with a reed switch (86) (see FIG. 3) mounted on bottom plate (12). In the closed position magnet member (20) is close enough to the reed switch (86) to magnetically toggle reed switch (86) and thus electrically toggle electrical circuit (100). When the magnetic apparatus (10) is moved in three-dimensional space so that reference plane (24) is changed with respect to gravity line (26) to a sufficient degree, then magnet member (20) will shift along slide axis (22) toward second magnet guide (18). Thus, magnet member (20) shifts from the closed position, as shown, to an open position where the magnet member (20) is shifted to the right (see FIG. 2). Magnet member (20) is weighted so as to provide more efficacious shifting yet with a smaller scale of elements for magnetic apparatus (10). Apertures (40), (54) provide open shifting of magnet member (20) as opposed to an enclosed compartment for shifting of magnet member (20), thereby averting problems of contamination and accumulated moisture content. In the preferred embodiment, five magnetic apparatuses (10) are combined in an array (84) (see FIG. 3) to provide a combination of thirty-two possible gravitational orientations, thus allowing an extremely gravitationally sensitive array which can be used in a system (110) (see FIG. 10) requiring a gravitation-detection component.