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POPULAR SCIENCE REVIEW. 
In concluding' these remarks on the different classes of 
parallel structure met with in rock masses in nature, the 
author would but state that his main object has been to direct 
the special attention of geologists working in the field to the 
extreme importance of studying carefully, not only the external 
contours, but the internal structure of rock masses also, in 
order thereby to avoid the mistakes which have been frequently 
committed ; such as recording as stratification planes which are 
in reality due to the effects of joints, cleavage, or foliation, or 
describing rocks of truly intrusive or eruptive nature as of 
sedimentary origin. 
