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THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



on pieces of 200- or 500-mesh screen. After drying, the screen is immersed 

 in chloroform to remove the last traces of plastic, and is then ready for 

 electron microscope use. 



The electron micrographs of Figs. 7-11 are presented as stereoscopic 

 pairs and enlargements of selected areas, the scale being given by dark lines 

 of 1 At length. Figure 7 is a micrograph from a chromium replica^" for which 



Fig. 7 — Chromium replica Qe = lOOA, da = 30**) of surface of a thermistor flake. 

 Resolution about 50A. Granularity is due to plastic mold. 



ie = 100 A, da = vSO°. The shadows show that the azimuth of incidence was 

 to the right at about vSO° above the horizontal. The granularity evident in 

 the enlargement shows evidence of this direction, and may be ascribed to 

 plastic granularity, except for a few of the larger hills or pits which are 



*« J. Ames, T. L. Cottrell and A. M. D. Sampson, Trans. Far. Soc. 46, 938 (1950). 



This paper, which appeared while the present paper was in preparation, exhibits micro- 

 graphs of chromium and other metallic replicas of surfaces of crystals grown from solu- 

 tion. The characteristic surface structures reported are in some ways similar to those 

 of the sintered thermistor flakes here shown. 



