78 



(0*1> 



(120) 



Fig. 19. Etching figures on 

 {010} produced by acids. 



(111) 



(2U) 











(30?) 



(010) 



(Hi; 



Fig. 20. Etching figures 

 on {120} produced by acids. 



pletely symmetrical, both up and 

 down and to the right and left; 

 the most common form, which 

 is especially produced by more 

 diluted acids, is given in the 

 figure. 



(Fig. 19) By concentrated and 

 strong acids the form approaches 

 more nearly to the rectangular one. 

 s {120} also shows compara- 

 tively large and distinct figures, 

 which are commonly developed 

 as shown in the figure. 



(Fig. 20) They are convex on 

 both sides , but most strongly 

 curved towards the edge formed 

 with ^{210}; the greatest depth is 

 at the opposite side. By using strong 

 and concentrated acids are also here 

 produced figures bounded by more 

 straight lines and approaching to the 

 form of a lengthened isosceles triangle, 

 or a lengthened trapezium. 



Л {210) is not corroded to so 

 high a degree as the preceding plane. 

 As to form the figures somewhat ap- 

 proach the last-mentioned, but are 

 more rectilinear, and more sharply 

 bounded on both sides ; 



(Fig. 21) These figures are also 

 more strongly curved to the left, to- 

 wards the edge formed with Л {2 10/. 

 г<'{301} is one of the most slightly 



