Analysis by the Electron Microscope 141 



feedback stabilizers, such electron spectographs can have resolu- 

 tions of the order 10"^ or better. In Hillier's instrument a 



micrograph can be taken of the same object by switching off 

 the magnetic field which deflects the beam and focuses it on 

 the analyzer. The very small image of the electron source is 

 withdrawn for a short distance from the specimen, and projects, 

 without lenses, a magnified shadow of the object on a photo- 

 graphic plate. Such shadozv microscopes, first described by 

 H. Boersch,'" can have resolutions of the order of 200 A or 

 somewhat better.* 



* The micro-analvzer has been fiillv described b\- J. Hillier and R. F. 

 Baker. /. Applied Phys. 15, 663 (1944). 



