DALY: PHYSIOGRAPHY OF ACADIA. 89 
effects of all further complicated by possible down-warping along the axis 
of the Bay of Fundy. 
Of the four factors, glacial erosion may be safely excluded from the list 
of important causes on account of its insufficient amount. On the other 
hand, some sort of denudation has taken place. In the field it is clear 
that the edges of the upturned sandstones and conglomerates in all 
these embayed areas are truncated, and in such a way as to suggest 
excavation of once filled troughs rather than a down-warping of the 
general peneplain. 
There can be no doubt that abrasion of the Fundy shores by wind 
waves is enormously aided by tidal scour; in the Annapolis Valley at 
least, the wind wave could never have rivalled the tidal as an erosive 
agent. It is but natural to inquire as to the value of such tidal action 
in explaining the lowlands round about. If the present rate of retreat 
of the cliffs on the western shore of the Minas Basin were maintained, it 
is very possible, if not probable, that the sandstones of the Annapolis 
Valley as far as the source of the Cornwallis River would be reduced to a 
surface below the level of low tide before atmospheric erosion could pro- 
duce an ultimate plain of denudation over the same area (Plate 5). We 
know as a matter of fact that the basin has been considerably enlarged 
in Quaternary time. May we believe that the tidal currents working 
here, in the Annapolis Basin, in St. Mary’s Bay, in Chignecto Channel, 
and in Northumberland Strait, would, at the completion of the “tide 
eycle” already begun, succeed in producing a submarine plain of erosion 
comparable to the once continuous floor of the Annapolis, Colchester, 
and Cumberland lowlands? Might this be done before any serious 
damage had been caused to the present form of the harder rocks of the 
Southern Plateau? At present, we can see no reason why these ques- 
tions should be answered in the negative. Hence, we must conclude 
that. if the conditions of the time of excavation were like those of the 
present, these lowlands, although in part the result of subaerial ero- 
sion, might have been to the greater extent produced by tidal scour 
operative at first in a number of rias, and then, at the close of the tide 
cycle, in a long sound stretching from what is now the Bay of Fundy to 
Northumberland Strait. 
But it must be remembered that, if our theory of the upland facet be 
correct, the constructional shore-line at the beginning of the second cycle 
was far removed from the existing one. St. Mary’s Bay did not exist 
then. The Bay of Fundy extended no farther to the east than what is 
now Digby Gut, and it was narrower than now. The amount of work to 
