R. XLIV W. 



R. XI, IV W. 



R. XLIII W. 



FIG. 1. Geological map of a portion of the Porcupine Mountains, Mich. 



2. Quartz-porphyry. 3. Diabase, Diabase-amygdaloid ("Trap")- 4. Sandstone and Conglomerate. 5. Diabase and 

 Diabase-amygda.oid ("Trap") 6. Sandstone with thin bands of conglomerate. 7. Dark-grey Sandstone and Black Shale. 

 (After Irving). 



