Explanation of Plate. 



Fig. 1. Geological Map of the environs of Uecla. 



Fig. 2. x 38. A slide of piedmontite-rhyolite, showing the formation of pied- 

 montite as a secondary product in the feldspar-phenocrysts. The 

 feldspar-crysts also kaolinised. Porphyritic quartz showing many inlets 

 of the ground-mass. 



Fig. 3. Piedmontite needles, obtained by pulverising crystal aggregates in drusy 

 cavities. Greatly magnified. 



Fig. 4. Intergrowtli of common epidote with piedmontite within a space formerly 

 occupied most probably by a porphyritic crystal of feldspar. Greatly 

 magnified. 



Fig. 5. Piedmontite and epidote in zonal arrangement, developed in a lateral direc- 

 tion. 



