ETCH TECHNIQUE 15 



according to those of the proposed "I. R. E. Standard."^ Figure 5.4 shows 

 the relation of these conventions to the natural faces of right and left quartz, 

 to the electric charges developed on compression and tension, and to the 

 more common cuts of oscillator plates. Also given are the relations of 

 handedness to the conoscope and the polariscope means of detecting handed- 

 ness (Section 2.7, Chap. II describes these instruments). It is important to 



Fig. 5.2— E.xamples of ELECTRIC.\L twinning alone. Electrical twins are com- 

 monly large, and hence may be cut apart and used individually. 



note that AT and CT plates are always cut at such an angular sense, relative 

 to the Z and X axes, as to be roughly parallel to a minor pyramidal face, 

 whereas the BT and DT plates are roughly parallel to a major pyramidal 

 face. Thus a stone exhibiting these faces may be cut into any of these plates 



« "Proposed Standard Conventions for Exi^ressing the Elastic and Piezoelectric Proper- 

 ties of Right and Left Quartz", Proc. I. R. E., Xov. 1942, p. 495. 



