The American Geologist, VriL. XXXIV. 
Plate VI. 
Thin sections of orbicular gabbro of second variety. .'\. Section of periphery, 
showing feldspar zone and concentric rings of olivine, which has here 
altered to actinslite. X 33. B. Section of periphery, with 
X Nicols, showing irregular orientation of feldspar X 33- 
