FOREWORD TO THE AMERICAN EDITION 



THE progress in electron microscopy since the closing of 

 the manuscript for the first British edition was both 

 extensive and intensive. The several hundred papers which 

 have appeared in the meantime on applications of electron micro- 

 scopes hardly give an idea of the extension of their use, as an 

 ever increasing proportion of the instruments is tied down in 

 routine work in hospital and factory laboratories, and the times 

 are long past when almost every successful micrograph was 

 published. No attempt was made, or could be made, to give 

 a full account of this extensive development in the limited space 

 of this monograph. On the other hand I have tried to give a 

 fair and up-to-date report on the basic progress, and I have 

 revised the first edition in every point relating to the theory of 

 image formation, wherever the views formerly expressed re- 

 quired alteration. Here, I must express my indebtedness to Dr. 

 James Hillier of the RCA, for a correspondence which has 

 greatly clarified my views, and led to the discovery of phase 

 contrast as a new factor in image formation. I am also very 

 thankful to Dr. J. Hillier and Dr. E. G. Ramberg for allowing 

 me to see the manuscript of their outstanding paper on "The 

 Magnetic Electron Microscope Objective: Contour Phenomena 

 and the Attainment of High Resolving Power," which describes 

 the ingenious methods by which these authors have now almost 

 completely bridged the gap which at the time of the first edition 

 still separated the practical performance of the electron micro- 

 scope from the theoretical limit. 



A short report on new commercial electron microscopes has 

 been added, and I wish to thank Prof. Louis de Broglie, Paris, 

 for allowing me to include a note on the work which is carried 

 out under his general direction on that most intriguing new 

 instrument, the proton microscope. 



D.G. 

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