Plate 23. 



"""W^ 



Porphyricic phase of the Purcell Lava ; from summit of the McGillivray 

 Range. Three-fourths natural size. 



Quartz amygdule in the Purcell Lava. The amygdule, tubular in form and here six 

 inches long, is partly weathered out of its rocky matrix. A part of it, of unknown 

 length, has been lost during the weathering of the lava. About one-half natural size. 



25a— vol. ii— p. 208. 



