Accurate neutralization of the earth's magnetic fieldBeover a long cylindrical region is necessary to extend the energy range of a magnetic‐lens spectrometer to electrons of very low energy. Axial conductors spaced 45° apart on the surface of a circular cylinder of radiusaare used to approximate a cos&thgr; distribution. The conductors at &pgr;/2 are missing since cos&thgr; vanishes. There are 1/√2 as many conductors at ±&pgr;/4 and ±3&pgr;/4 as at 0 and &pgr;. In the plane transverse to the length of the cylinder, the radial variation of the compensating field is given approximately by the termBe(r/a)6cos6&thgr;. Beta‐rays of a few kilovolts energy, which reach a maximum radiusa/2, experience an average residual field of about 0.1 percent ofBewhich produces a deflection of about 0.1 mm for a one‐meter spectrometer. The construction of the coils is described.