An "orthogonal mechanical scanner" is described here which makes the time consuming and tedious task of visual scanning of nuclear emulsions and solid detector plates in special cases obsolete. With this instrument in about 120 min a plate of 2.5×7.5 cm 2 can be scanned completely in 10μm wide stripes with a velocity of 2.8 cm/sec. The advantage of this instrument is the electronic pulse-length-discrimination which makes it unnecessary to use several photomultipliers and several channels of discriminators. The handling of the instrument as well as the particle identification thus is very much simplified. The instrument is used to scan the mass spectrum of fission particle tracks in nuclear emulsions as well as in solid detectors.