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A large double magnetic lens spectrometer has been constructed for the study of gamma- and beta-ray spectra. The magnetic field is produced by two identical coaxial water-cooled coils, each 10.2 cm wide, 31.7 cm I.D., 73.7 cm O.D., and spaced 95.6 cm apart. The source is placed on the axis at the center of one coil and the detector is placed on the axis at the center of the other. The instrument is characterized by a large transmission with moderate resolution. Scattering is virtually absent because of the nature of the trajectories which are used, and because the large dimensions have made possible the removal of scattering material to a considerable distance from the source. The design has lent itself easily to the application of accelerating voltages at the detector admitting the detection of beta-rays down to 1 kilovolt. The maximum energy conveniently studied with the present arrangement is 2.8 Mev. Beryllium-coated Zapon films of thickness 0.01 mg/cm2 have been used to mount sources. Charge does not accumulate on these sources. Observations with a Cs137 source 4 mm in diameter have shown a transmission of 1.4 percent with a resolution of 1 percent. The appearance of the internal conversion and Auger electron lines testifies to the absence of appreciable scattering.