REPLICA AND SHADOWING TECHNIQUES 



opposition to minimize the over-all rotation 

 of the image. The relevant formulas and 

 tolerances in the correction settings are given 

 in a paper by Page (1958b).. The tolerances 

 in the alignment of the objective aperture 

 (which must be accurately centered) are 

 also given in this paper. 



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Michael Seal 



REPLICA AND SHADOWING TECHNIQUES 



Nowadays there are very few types of 

 specimen which cannot be examined in the 

 electron microscope. Internal structure can 

 be studied by means of thin sections, and 

 surface topography by replication or shadow- 

 ing. It is with the latter that this article is 

 concerned. Many replica and shadowing 

 methods described in the hterature are com- 

 phcated, hence only the principles of the 

 basic techniques will be described here. 



Many specimens which are small enough 

 to be examined directly in the electron micro- 

 scope are opaque to electrons, so that the 

 image produced consists of silhouette. Large 

 specimens cannot be examined directly ex- 

 cept by means of reflection electron micros- 

 copy. Thus it can be seen that a study of the 

 surfaces of most objects demands special 

 techniques if examination is to be in the 

 electron microscope. These techniques con- 

 sist of the preparation of replicas. A good 

 replica must faithfully reproduce even the 



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