98 



The Electron Microscope 



amplifier. The multiplier receives on its photo-cathode the vary- 

 ing light intensity emitted by the fluorescent screen. The second 

 artifice is to reduce the frequency band AF of the amplifier to 

 300 cycles, and take the micrograms extremely slowly, in about 

 8-10 minutes, so as not to lose any details of the picture. The 

 amplifier operates on a facsimile recorder, which can be seen 

 at the right of figure 36, and which prints a seven hundred fifty 

 lines image every 10 minutes. Figure 37 is a sample of a scan- 

 ning micrograph. The resolving power is of the order of 500 A, 

 which is sufficiently below the resolution limit of the optical 

 metallographic microscope to promise the new instrument a wide 

 and useful field of application. 



Fig. 37. Scanning electron microgram of the surface of slightly an- 

 nealed brass obtained with R.C.A. scanning electron microscope. 

 Magnification X 5,000 



