EXTENT OF THE REGION. 235 
degrees may be observed in Huronian schist resting on gneiss at the 
south of the batholite, and basic schistose rocks found in its interior 
west of Astron bay are perhaps remnants of the upper parts of the low 
arch of the dome. 
‘In other cases where the dip of the schist is very steep or sometimes 
even tilted a little under the edge of the batholite, it is probable that the 
dome was much higher, and the stretching of the overlying strata must 
have amounted even to miles in large domes like that of Rainy lake. 
EXTENT OF THE BATHOLITIC REGION 
The region whose geological history has just been sketched extends 
from the lake of the Woods on the west to lac des Mille Lacs on the east, 
a distance of more than 200 miles, with a width north of Rainy lake of 
120 miles. Most of this large extent of country shows the mesh struc- 
ture in a more or less typical way, though toward lac des Mille Lacs on 
the east the bands of Huronian tend to become parallel, suggesting an 
approach to the more normal folded mountain structure. Throughout 
this whole region the Laurentian has eruptive contacts with the Huro- 
nian, and nothing like a basal conglomerate of the Huronian can be 
found.* 
It would be unwarranted perhaps to suggest that the relationships de- 
scribed are normal for the Archean, especially when relatively only a 
small portion of the immense extent of the Canadian Archean has been 
mapped with any detail, yet in a considerable number of instances similar 
relationships have been found. 
Dowling maps imperfect mesh-like strips of Huronian about areas of 
eruptive gneiss and granite from the district of Keewatin + 80 miles 
north of the lake of the Woods, and Barlow states that the underlying 
eneiss has an eruptive contact with the Huronian in the Sudbury region 
500 miles to the east of lac des Mille Lacs. Dr Bell, however, appears to 
differ from this view, explaining the relation of the two series of rocks, 
at Wahnapitae for instance, by assuming a fault.{- My own observations 
near Sudbury and Wahnapitae convince me that at those points the con- 
tact is eruptive, since dikes of pegmatite, etcetera, may be seen passing 
*Van Hise (Pre-Cambrian Geology, p. 786) follows Smyth in speaking of the Steep Rock Lake 
series as resting with a characteristic basal conglomerate on the eroded edges of the Basement 
Complex ; but my own observations show this to be no exception to the generalrule. The gneissoid 
granites which enclose the series form eruptive contacts with the Keewatin at the Harold Lake 
gold mine a few miles west of Steep Rock lake; and Smyth himself (Am. Jour. Sci., vol. xlii, 1891, 
p. 322) in describing the supposed basal conglomerate states that it contains large pebbles of quartz 
and greenstone, but mentions no gneiss or granite pebbles. 
+ Geol. Survey of Canada, 1894, part F. 
} Ibid., 1890-91, p, 14, F. 
