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BELL SYSTEM TECHNICAL JOURNAL 



into a strong spur. The spur reaches its maximum development at 

 54 volts in colatitude .SO degrees, then decreases in intensity', and 

 finally vanishes from the curve at about 70 volts in colatitude 40 

 degrees. 



We next make an exploration in azimuth through this spur at its 

 maximum; we adjust the bombarding potential to 54 volts, set the 

 collector in colatitude 50 degrees, and make measurements of the 

 intensity of scattering as the crystal is rotated. The results of this 

 exploration are exhibited by the curve at the bottom of Fig. 3, in 

 which current to the collector is plotted against azimuth. We find 

 that the spur is sharp in azimuth as well as in latitude and that it is 

 one of a set of three spurs as required by the symmetry of the crystal. 



We observe also that there are small spurs showing in the B-azi- 

 muths. We turn the crystal to bring the B-azimuth under observation, 

 and again make explorations in latitude for various speeds of bombard- 

 ment. We find that the spur in the B-azimuth is similar to the 

 "54 volt" spur in the A-azimuth, but that it attains its maximum 

 development at a higher voltage and at a higher angle. Curves 

 exhibiting its growth and decay are shown in Fig. 4. Maximum 



50 

 VOLTS 



B 



AZIMUTH 



58V. 62 V 65 V. 66 V. 68V. 



AZIMUTH CURVE FOR [e= 44 » V = 65 VOLTs] 

 Fig. 4 — Similar for the B-azimuth 



development is attained at 65 volts in colatitude 44 degrees. At the 

 bottom of the figure we show the intensity-azimuth curve through 



