350 TRANSACTIONS OF THE CANADIAN INSTITUTE.” [Vou. VIII. 
The quartz-diorites of the region may not be of the same age as these 
other greenstones, but as they cannot be classed by themselves, they are put 
in here. They are most plentiful west and south of Wendigokan Lake, 
and appear as rounded or irregular masses. No thin sections of these 
were made, but I found a typical quartz-diorite pebble in the Huronian 
conglomerate, and it will be mentioned in connection with that rock. 
As already stated these diorites may be of Laurentian age. The green- 
stones are not as widely distributed as the green schists and are most 
common south of Lake Wendigokan. These rocks have been the origin 
of some of the schists which grade into them, but portions of them have 
resisted the shearing action and largely retained their original massive 
condition. They have also exerted quite an influence upon the strike ' 
of the schists in their neighbourhood. 
THE BANDED SLATES AND ARKOSES. 
The slates are widely distributed but in small masses. They almost 
invariably occur with the iron range and although a good indication of 
the presence of that formation in the immediate neighbourhood, they 
may occur without it. On account of their very intimate connection 
with the iron range, it is difficult to say to what extent they should be 
considered a part of it. They are black or sometimes grey on the weath- 
ered surface, and are made up of argillaceous deposits. They occur 
interbanded with streaks of the jasper and banded silica, and interbanded 
with the silica or jasper which conditions show that there was probably 
a frequent change from a predominance of chemical sediments to that of 
mechanical sediments during the formation of the iron range. And the 
interbanding of the slate and arkose shows that there were frequent varia- 
tions in the coarseness of the mechanical sediments. This might be 
accounted for by supposing the attitude of the land to the sea changed 
frequently, that the rate of disintegration of the rocks of the land varied 
often, or that the strength of the currents of the Keewatin rivers was not 
uniform at different times. Since these deposits occurred in bodies of 
shallow water, I think that the banding is due chiefly to the difference 
in the strength of the currents of the streams at different times and partly 
to the variation in the rate of weathering the land surface, which varia- 
tion might be due to change of climatic conditions, and with that the 
change in the amount of vegetation which may have covered the land 
surface at that time. 
A thin section of a specimen taken near the jasper in location HF 38 
shows interbanded slate and arkose. The slate is too fine-grained to show 
many distinctive features, but it contains considerable pyrite in very 
