“…This name is given to the spectrographs in which an analytical line is excited by an electron beam in a volume that may approach 1-micron cube. These instruments permit of reliable and convenient point-to-point exploration on a micron scale, and they can thus provide information attainable 101,117,122,159,160,163,182,186,192,193,198,202,218,220) Krypton in no other way. The instrument invented by Castaing {132) is now offered commercially {104), and two recent articles {40, 173) give a variety of interesting applications.…”