Momentum spectra of charged particles are often analyzed with the aid of magnetic focusing; in one type of spectrometer the particles move along a circular arc roughly perpendicular to the lines of force. It is shown that when the beam is turned through an angle of radians in a suitably shaped magnetic field a two-directional focus is obtained. For this type of instrument the dispersion increases rapidly as n is increased, while the aberrations remain roughly constant. Even for values of n in the range 3 to 7 an enormous gain in "luminosity" and a useful increase in the permitted source width should be obtained. Although practical difficulties are introduced by the use of paths of more than one complete revolution, these should not be insuperable if the size of the apparatus is large enough relative to the size of the source, especially if an odd value of n is used.