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BELL SYSTEM TECHNICAL JOURNAL 



obtained are not aligned with the electric axes of the specimen. They are 

 shifted approximately 12° therefrom, and in opposite directions for the right 

 and left varieties. Figure 5.11 shows a section of right quartz so positioned 

 on the sliding table that the etch-figure therefrom will be properly aligned 

 with three radial lines of the viewing screen. The section need not have 

 natural faces as here shown. With the section so positioned the sliding table 

 is moved over the right-hand marking template, and the section is marked 

 with three radial lines. These lines on the section then give the approximate 

 direction (within 5°) and the sense of the three electric axes of the quartz, 

 positive X-outward. With left quartz the etch-figure is still aligned with 

 the same lines on the viewing screen, but the section is marked through the 

 left-hand marking template (the marking having the same meaning as be- 



;SLIDING TABLE 

 QUARTZ 



SIDE 

 VIEW 



MARKING 

 TEMPLATE 



TOP VIEW 



SCREEN 

 VIEW 



MARKING 

 TEMPLATE 



Fig. 5.11 — The reflection ORIASCOPE as applied to determining the direction and 

 sense of the X (electric) axes in Z-cut sections. After the etch-figure is aligned on the 

 screen the table and sections are moved over a marking template and the section marked 

 from below with axes. 



fore). The section so marked is ready for laying out the approximate cut- 

 ting directions, the sense of which may be found from Fig. 5.4. The exact 

 cutting directions are obtained by X-rays. It might be noted that ordi- 

 narily the handedness of the section is determined in the conoscope (see 

 Section 2.7, Chap. II) before examination on the oriascope. Also the twin- 

 ning boundaries are previously determined by examination of the etched 

 surface in a spot-light beam. 



Figure 5.12A, B show the type of etch-figures obtained on Z-cut sections 

 (in each case the figure is properly aligned with the rulings on the viewing 

 screen). The simpler etch-figure A is obtained on a fine ground (400 car- 

 borundum) surface by a weak etch (about 10 minutes in S0% HF). Though 

 the three faint spots, about 40° clockwise from the rulings (for the left-hand 



