BULL. GEOL SOC. AM. 



VOL. 16, 1904, PL. 58 



Figure 2.— The Same with Crossed Nicoi.s and Gypsum Plate. X 05 



PHOTOMICROGRAPHS OF HYPERSTHENE-GABBRO 



Two miles southeast of Bervvyn, Chester county, Pennsylvania. Photographed 

 F. J. Keeley 



