30 



SMITHSONIAN INSTITUTION 



Fk;. 2<j. — Part of one of the many enormous limestone quarries in the 



northern belt of southern Michigan. All equipment is electrified. In the 



foreground is a log barracade for the protection of quarrymen during the 

 noonday blasting. (Photograph by E. R. Pohl. ) 



Fig. 30. — Where fossils are legion. A blue shale has been thrown out of 

 the test pit in the foreground and in weathering has exhibited thousands of 

 fine shells. Quarry near Charlevoix, Mich. (Photograph by E. R. Pohl.) 



