PLATE XVIII. 
Fig. a. — Flow structure iu an aporhyolite. Specimen and slide loaned by Prof. S. 
L. Powell, of Newbury, S. C. From tbe South Mountain. In ordinary light, X 24. 
Fig. b. — Chain Sjdierulites in an aporhyolite. Specimen 34. Slide 34 D. From the 
neighborhood of the Bigham copper miue. In ordinary light, X 24. Quartz pheno- 
cryst (now granulated) inclosed by chain spherulites. Clear spherules in center of 
dark bands are still preserved. 
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