EXTENT OF THE REGION. Dox 
schists, etcetera, of Lawson in the Basement Complex, on whose eroded 
edges the Huronian is supposed to rest.* Asit seems generally assumed 
that distinctly clastic rocks, such as the little altered Couchiching sand- 
stone of Rainy river, should not be referred to the Laurentian, it might 
be well for a small party of American and Canadian geologists interested 
in these questions to go over certain typical regions together, so as to 
come to a common basis of classification for these difficult formations. 
However it may be in other regions, there is certainly a very large area 
in northwest Ontario in which the relations between batholites of granite 
and gneiss and the schistose rocks of Huronian (Ontarian or Algonkian) 
age are as described in the foregoing paper. Tens of thousands, if not 
hundreds of thousands, of square miles of the western Huronian were 
once afloat on a plastic granitic magma which swelled into great bubble- 
like mounds, while the colder surface rocks tended to sink into the spaces 
between ; and a phenomenon of such wide extent deserves careful study, 
whether the explanation given above be correct or not. 
It is worthy of note that in several regions where ancient sediments 
were supposed to rest discordantly on the Fundamental Complex more 
detailed study has proved that the contact is eruptive. The latest in- 
stance is described by R. A. Daly, who finds batholitic gneiss pushing 
through overlying mica-schist in New Hampshire.t 
It is probable that wherever sediments accumulate to a thickness of 
40,000 or 50,000 feet the beds on which they he become plastic if not 
fused, shift their place to correspond to the load, and form eruptive con- 
tacts with the rocks above. As this has taken place beneath every great 
mountain range, perhaps aided by relief from pressure under anticlines, 
and is no doubt still taking place where preparations are being made for 
the great mountain chains of the future, a so-called Fundamental Com- 
plex is to be regarded, not as characteristic of great antiquity, but as re- 
sulting from a certain set of conditions which may exist at any age. 
The older mountain ranges, having been more deeply eroded, give an op- 
portunity to study these gneissic and granitic cores, while in later ranges 
they are still buried out of sight. It is likely, however, that a basal sec- 
tion through our present mountain ranges would show long bands of 
gneiss and granite rather than approximately circular batholites, such 
as we find in western Ontario. 
If the supposition just made be correct, areas of the Laurentian or 
Fundamental Complex do not represent the earth’s erstarrungskruste 
but are merely portions of the earth’s crust, of sedimentary or other 
origin, which have been buried deeply enough for hydrothermal fusion 
* Pre-Cambrian Geology, p. 782. 
{Journal of Geology, vol. v, no. 7, p. 694, ete. 
