THE GOWGANDA LAKE DISTRICT, ONTARIO 673 



and this seems likely. Perhaps, also, water originally contained in 

 the sediment and, in this class, in large a"mount, takes an important 

 part in the transfer of material. 



SUMMARY 



I. The diabase of the Gowganda area occurs as sills and dikes 

 cutting the older formations. 



Fig. 5. — Photograph of polished specimen (natural size), showing light-colored 

 granophy re-rich "diabase" against dark-colored, brecciated slate (Foot Lake). 



2. The dike rocks are commonly porphyritic and oli vine-bearing 

 and never show distinct evidence of differentiation.- 



3. The sill rocks are never porphyritic; olivine is represented by 

 the more silicic enstatite; granophyric interstices visible in the hand 

 specimen as "red spots" sometimes occur. 



4. A typical granophyre sometimes occurs at the upper contact. 



5. The granophyre, like the granophyric interstices, is albite 



