Ichikawa — Etched Figures of Japanese Quartz. 461 



on the pole of the etched sphere as in tig. 2 B, indicating 

 a revolution of 60° about the vertical axis. Fig. 12 is the 

 same as fig. 11, and the striations on its section show numerous 

 regularly arranged ridges. 



Plate IV. 



Fig. 1, A, shows the outline of the sphere in fig. 1 of 

 Plate III : A, observed horizontally through both poles 

 of the vertical axis, the dotted hexagon showing the position of 

 the axes. B, is the same as A, but it is more etched, and its 

 outline resembles a trigonal trapezohedron as in Plate II, fig. 1, 

 D ; the dotted circle shows the original outline of the sphere. 

 B', is a front view on h h' of the negative end of the lateral 

 axis (compare (x) in fig. A). C, is more etched than B, and 

 shows that a part of the negative end of the lateral axes at the 

 external part of the dotted circle (n) is just about separated 

 from the direction of the intermediate axes ; the structure in 

 the internal part of the circle corresponds to the structure of 

 Plate II, fig. 1, D. C 7 is the same as B'. D, shows a sphere 

 more etched than C ; the part within the dotted circle (n) 

 successively repeats the action as in fig. C, and gradually 

 dissolves away. Fig. 2, A, those in Plate III, fig. 2, A, and 

 B, B', C, C and D correspond to B, B', C, C, and D of fig. 1. 



Fig. 3 shows horizontal projections of the trapezohedral 

 elevations formed on the base-like face of (a o c) at a pole of the 

 etched sphere, A, left and B, right. Fig. 4 shows horizontal 

 projections of these negative and positive trapezohedral eleva- 

 tions formed on base-like faces (a o e) at a pole of the etched 

 sphere, A, left and B, right. Fig. 5 shows, magnified, the indi- 

 vidual elevations of figs. 3 and 4, and has pits of 7-like shape on 

 its faces: the dotted hexagon shows the position of the axes, A, 

 left and B, right. Fig. 6 is more etched than fig. 5 and has a 

 rough base-like face ; the ridges are a little twisted to the left 

 or right of the vertical axes. Fig. 7 is still more etched, the 

 ridges being very much twisted like a left-handed or right- 

 handed distorted quartz. 



Fig. 8 shows the trapezohedral elevations with regularly 

 developed base-like face. Fig. 9 shows the pole edges trun- 

 cated by a trapezohedral face with different coefficient from 

 itself. Fig. 10 shows forms of peculiar shape very rarely 

 observed. 



Fig. 11 shows the etching figures formed on a plate cut per- 

 pendicular to the vertical axis of a Brazilian twin, revealing the 

 direction of rotation, and in the section, each area of the left 

 (I) and right-handed (r) crystals is indicated as distinctly as in 

 polarized light. Fig. 12 shows a Dauphine twin as fig. 11. 



