386 



JAMES HILLIER 



Fig. 2. Photograph of a modern electron microscope with doors and covers 

 open, showing actual operating components. 



the exciting winding, the operator can vary the focal length of such 

 a lens over a wide range. This means that it is not necessary to 

 move the lenses of an electron microscope to focus the instrument. 

 Nor is it necessary to replace eye lenses or objectives if different 



