390 JAMES HILLIER 



2. Fimdanienlals of Application of the Electron Microscope 



In the preceding section the fundamental principles involved in 

 the design and operation of the electron microscope have been set 

 up in the most elementary form possible. To the scientist, whether 

 he be biologist, chemist, or metallurgist, who wishes to apply the 

 electron microscope in his own particular research, that description 

 is of academic interest only. Actually, he needs comprehend only 

 one fact, namely, that the electron microscope is a device for pro- 

 ducing a visual image of the microscopic structure of the material 

 he is studying. In fact, the use of electrons distinguishes this instru- 

 ment from other microscopes only insofar as it permits the observation 

 of finer structures in the same way that light microscopy is distin- 

 guished from ordinary vision by the dimensions of the structure 

 examined by that method. Thus, in its true sense, electron micros- 

 copy is merely a term defining the simple use of our ordinary sense 

 of vision in research involving a very fine scale of dimensions. 



To state that our sense of vision is one of our most important assets 

 in research would seem platitudinous. At the same time our sense 

 of vision has been so much a part of our environment that we are 

 sometimes inclined to forget that the eye-brain combination is an 

 almost fantastic device capable of measuring and recording in the 

 space of one-tenth of a second the intensity, wavelength, and position 

 of over a million points of light. By way of comparison consider the 

 indirect scientific method of investigating, saj^, an everyday scene. 

 Actually such an analysis is carried on electronically in a television 

 camera, where the intensity of each point of the scene is measured 

 and converted to an electrical oscillation of a corresponding ampli- 

 tude. The scientific data in this case would consist of a long list of 

 several million numbers representing the amplitude of that electrical 

 signal at regular intervals, say, every ten-millionth of a second. The 

 manual conversion of such data into a form that would reveal the 

 desired information regarding the original scene would, of course, 

 involve a prohibitive amount of labor. Thus, the data are valueless 

 unless electronic means are used for reconverting and presenting 

 them in the form of a visual image, which is then comprehended im- 

 mediately. 



The data obtained by a research worker using indirect methods to 

 investigate a heterogeneous system on a microscopic scale are quite 

 analogous to the tabulated data representing the television image. 



