20 
MUSEUM BULLETIN NO. 18. 
however, later writers on palaeogeography have accepted and 
followed more or less closely Dana’s delineation of the permanent 
character of the Azoic continent. A few geologists have not 
accepted this view. Lawson, after reviewing the available 
evidence, concludes that “the surface of the Archaean ‘nucleus’ 
was once very extensively if not wholly covered by Palaeozoic 
sediments.” 1 Willis should also be noted as opposing it. He 
states, in speaking of the Archaean protaxis, that “It was sub- 
merged probably beneath the general Cambro-Ordovician 
transgression and certainly to a great extent beneath the Siluro- 
Devonian seas which spread over Arctic Lands.” 2 Most of 
the maps of the Palaeozoic seas make their shore-lines more or 
less coincident with the north side of the St. Lawrence and Ot- 
tawa rivers. The recognition of the Laurentian escarpment 
as a fault plane, however, leaves no ground whatever for con- 
tinuing to draw palaeogeographic strand lines at or near this 
line. A diagrammatic restoration of the relations of the 
Archaean of the Laurentian plateau and the Palaeozoic 
of the St. Lawrence lowland, which existed before faulting, 
will show that 2,000 to 4,000 feet of Palaeozoic rocks overspread 
the southern border of the present Laurentian highland. Such 
a considerable thickness of sediments overlapping the Archaean 
points unmistakably to a very considerable extension, toward 
the north and beyond its present margin, of the seas of Palae- 
ozoic time. 
A partial reconstruction of the Montreal section as it existed 
previous to the extensive denudation which has developed the 
Palaeozoic plain is highly Instructive in this connexion. A remnant 
of horizontal Trenton limestone is preserved on the slopes of 
Mount Royal, the highest beds having an elevation of about 
500 feet. The thickness of the Utica- Lorraine in the region 
adjacent, according to Adams and Leroy, 3 is about 2,300 feet. 
This is doubtless a conservative figure since Foerste, in the region 
to the northeast, gives these beds a considerably greater thick- 
1 Bull. Geol. Soc. America, Vol. I, 1890, p. 172. 
2 A theory of continental structure applied to North America, Bull. 
Geol. Soc. America, Vol. 18, 1908, p. 394. 
•Ann. Rept. Geol. Surv., Canada, new ser., vol. XIV, 1901, p. 270. 
