INORGANIC REPLICATION IN ELECTRON MICROSCOPY 809 



probably due to features of the original surface. Resolution ranges upward 

 from about 50 A. 



The detection of films in shadows is difficult when these films are so thin 

 as to approach the minimum perceptible thickness difference. The film may- 

 be flawless and present, or ruptured during processing and completely 

 eliminated, and the difference between these two conditions is difficult to 



Fig. 8 — Chromium replica (h = 150A, da = 30°) produced by two evaporations differ- 

 ing in azimuth by 90°. Region within the circle shows partial shadows. 



discern. Only when structure or edges due to partial rupture appear is it 

 easily detectable. Some shadows in the rephca from which Fig. 7 was made 

 showed such a fikn, which was estimated to be less than 10 A in thickness, 

 but in most of the shadows no evidence of a film could be seen. 



A chromium replica produced by two evaporations, from azimuths 90° 

 apart, was the subject of the micrograph of Fig. 8. This repHca was not 

 washed in chloroform, which accounts for the presence of the residual 

 plastic rings. This particular micrograph was selected to show the partial 



