418 E. S. MOORE 
more rarely chalcopyrite is found. In one large sill a mass of 
impure dolomite has been inclosed, partly altered to tale and 
serpentine and impregnated with chalcopyrite. There is not 
sufficient copper, however, to be of economic interest. 
The occurrence of cobalt in a calcite vein in one of these sills 
is interesting because of its frequent association with the Keweena-_ 
wan diabases in other parts of Canada. A narrow vein of calcite’ 
was found cutting the basalt and carrying smaltite, chalcopyrite, 
magnetite, actinolite, and specular hematite. 
The relation between the igneous rocks and the sediments is 
not always clear. In most cases it is quite evident that the former 
are distinctly later than the latter, but in the case of the large mass 
of diabase and basalt forming the backbone of Tookcarak Island 
the evidence is inconclusive. It would appear that the sediments 
above it have been metamorphosed to some extent, but this cannot 
be proved to be the result of contact action. 
There are some amygdules of chlorite in its upper portion, but 
no sign was seen of ellipsoids, so common in some of the distinct 
flows in the area. Although amygdules are usually considered 
evidence of extrusion, they cannot be taken as definite evidence of 
such origin because vesicular dikes and sills are known which must 
have solidified thousands of feet below the surface. The question 
of whether an intrusive rock will be amygdaloidal or not depends 
chiefly upon the porosity of the rock adjoining it, and on the amount 
and pressure of the gases which it contains. Leith regards some of 
the sheets in the Richmond Gulf region as flows, but so far the 
writer has not found any of these interbedded igneous masses which 
he is sure are flows. There is one great extrusion, however, which 
is the youngest consolidated rock seen on the Belcher Islands, and 
which apparently at one time spread over the whole of the islands. 
It seems probable that it also extended to the Manitounick Islands 
near the coast of the bay. It immediately overlies the main band 
of iron-formation at almost every point where it outcrops. Its 
thickness is uncertain, since the flow is largely under water, but it 
is doubtless several hundred feet. Near Kasegalick Lake it is 
about 30 feet, but this does not represent its maximum thickness, 
since it has suffered much from erosion (Figs. 3, 4,5). This extru- 
