92 



The Electron Microscope 



5,000 A). One of the most interesting is the polystyrene-siHca 

 method of Heidenreich and Peck,*^^ which was used in reproduc- 

 ing the calcite surface in figure 34a. The specimen is first 

 molded into polystyrene, and this is coated by evaporated quartz. 

 The most surprising effect was discovered, namely, that as 

 long as the layer is thin enough, the silica molecules spread on 

 the polystyrene like a liquid and form a perfectly smooth outer 

 surface. After dissolving the polystyrene mold, the silica film 

 can be introduced into the electron microscope. 



Fig. 34a. Electron micrograph of polystyrene-silica replica of a freshly 

 cleaved calcite surface, obtained by R. D. Heidenreich, Dow Chemical 

 Company. 



(By courtesy of Dr. V. K. Zworykin, Associate Director of R.C.A.) 



