A new type of pair spectrometer is described. The rotation of the image in a short magnetic lens is used to separate negatrons and positrons by putting the pair converter a little aside from the optical axis of the lens. It is then possible to obtain coincidence ``lines.'' The apparatus has been tried on the 2.62‐Mev &ggr;‐ray of ThC″ and the 2.76‐Mev &ggr;‐ray of Na24.