Simpler Methods in Crystallography. 



359 



Explanation of Plates X., XL, XII. 

 Plate X. 



A Gnomonogram of Quartz, giving most of the recognised forms, " Dana's 

 Symbols." By J. G. Goodchild. 



Plate XL 



A Stereogram of Barytes; c, Projection; giving most of the forms yet 

 described, and some that are new. "Dana's Symbols." By Wilbert 

 Goodchild. 



Plate XIL 



Stereograms of Orthoclase; b aid c, Projections. "Dana's Symbols. 

 By J. G. Goodchild. 



