1907-8.] THE GEOLOGY OF THE LAKE WENDIGOKAN REGION, 359 
excluded from view by drift, where it comes in contact with the iron 
range in locations HF 13 and 14 the diabase has the appearance of having 
flowed out over the older rocks leaving them little disturbed, as the iron 
range does not appear to have been bent up and the diabase seems to lie 
on topofit. If it were a sheet it would grow finer grained toward the top, 
which it does not do over much of the outcrop, though it is probable 
that a great deal of material has been eroded from its surface and the 
portions of the mass now remaining are quite below the original surface. 
There are no evidences of scoriaceous, vesicular, amygdaloidal or pillow 
structure which would suggest a surface flow, but on the contrary much of 
the rock is quite coarse grained. Considering the irregular form of the mass, 
Diabase Hills on the Nipigon River. 
its general irregular surface, when contrasted with the level surface of 
the diabase sheets farther south along the Nipigon River, though there 
are flat areas on top, the failure of the rock to grow fine-grained towards 
the surface, the lack of columnar jointing so common in the silts of the 
region, and the general relations between the eruptive and surrounding 
rocks, I think it can safely be called a batholith or bysmalith, more nearly 
the former than the latter. 
