ETCH TECHNIQUE 



35 



to an area directly over the bottom surface. This restriction may be elim- 

 inated, and no flat bottom surface need be used at all, if the bottom surface 



RHQ +X UP 



RHQ -X UP 



LHQ-XUP 



B 



LHQ+XUP 



BT 



marking template 

 (for a) 



MATCHING WINDOW 



MARKING TEMPLATE 

 (for B) 



Fig. 5.19 — Etch-figures obtained with the pin-hole oriascope in X-cut sections. After 

 an etch-figure is aligned with the rulings on the matching window, as in C, the section is 

 marked thru a marking template fin this case the one on the left) with the direction of the 

 Z axis and the direction of cut of the desired plate (in this case the BT). 



of the section be immersed in a transparent dish of immersion fluid (whose 

 refractive inde.x matches that of quartz) placed over the pin-hole. Here the 



