1. A GAS CELL ARRANGEMENT COMPRISING, IN COMBINATION: A BODY MEMBER HAVING WALLS DEFINING A CAVITY AND SAID WALLS TRANSPARENT TO MAGNETIC ENERGY AND PRESELECTED WAVELENGTHS OF ELECTROMAGNETIC RADIATION; A FIRST RESONANT MEDIUM CONTAINED WITHIN THE CAVITY AND SAID FIRST RESONANT MEDIUM EXHIBITING A POSITIVE NET MAGNETIC MOMENT; A SECOND RESONANT MEDIUM CONTAINED WITHIN THE CAVITY AND SAID RESONANT MEDIUM EXHIBITING A NEGATIVE NET MAGNETIC MOMENT; MEANS FOR ALIGNING SAID NET MAGNETIC MOMENT OF SAID FIRST RESONANT MEDIUM AND SAID NET MAGNETIC MOMENT OF SAID SECOND RESONANT MEDIUM IN A FIRST DIRECTION; MEANS FOR INCLUDING A PRECESSION OF SAID NET MAGNETIC MOMENT OF SAID FIRST RESONANT MEDIUM AND SAID NET MAGNETIC MOMENT OF SAID SECOND RESONANT MEDIUM ABOUT SAID FIRST DIRECTION IN A MANNER SUCH THAT THE NET MAGNETIC MOMENT OF SAID FIRST RESONANT MEDIUM PROSESSES IN A FIRST ROTATIONAL DIRECTION AND SAID NET MAGNETIC MOMENT OF SAID SECOND RESONANT MEDIUM SIMULTANEOUSLY PRECESSES IN A SECOND AND OPPOSITE ROTATIONAL DIRECTION; AND MEANS FOR DETECTING THE PRECESSIONAL ROTATION RATES OF THE NET MAGNETIC MOMENTS OF SAID FIRST AND SAID SECOND RESONANT MEDIA.