90 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
be done in excavating a submarine platform of erosion in the sandstones 
was thus vastly greater, both as to thickness and area, than the amount 
required to complete the present “tide cycle.” Moreover, the tidal cur- 
rents would be much less powerful than now, both at the beginning and end 
of the longer cycle ; they would probably be similar to the tides of the 
Maine shore in the first stage and not much higher in the last. Chal- 
mers (98, p. 19) has calculated that, if the Chignecto Isthmus were sub- 
merged, the tides would not average more than 10 or 15 feet in range, 
giving a ratio of scour for the corresponding currents not much greater 
than in Massachusetts Bay. Yet the isthmus must have been submerged 
if the Triassic and Carboniferous lowlands were in reality due chiefly to 
tidal scour. Destroying the conditions of the present unusual tides, 
more normal flood and ebb currents would be called on to do work on a 
scale that has not been paralleled elsewhere. 
Such submergence obtained during the Saxicava Sand period. The 
Fundy region was then depressed “at least” 120 feet according to 
Chalmers (’95, p. 18), 220 to 225 feet according to Dana.!_ Correspond- 
ing to our deduction, the “ Champlain” sea-floor, revealed in the exist- 
ing deposits at Middleton, shows evidence of relative quiet. Their wide 
extent seems to indicate that tidal scour was then powerless to remove 
unconsolidated material from the floor of the Annapolis Valley, much 
less excavate the Triassic sandstones. Even more striking is the occur- 
rence of similar sands in Sandy Cove and on the slopes of the Petit Pas- 
sage, in each of which there is a heavy tidal rip. Ebb and flood currents 
must have been weak in those days. But, weak as they were, the con- 
ditions were certainly more favorable to scour than they would have 
been if there had been no open funnel-like Bay of Fundy to furnish 
concentration. 
Now, in addition to the fact that we do not know how much ability 
for excavation on the part of the tides is at our disposal during the time 
elapsing after the warping of the peneplain, we have the second great 
difficulty that we do not know the exact form of the Bay of Fundy 
when the warping was finished. We might imagine that during the long 
period of the previous cycle, tidal currents had conspired with atmos- 
pheric erosion to open a channel from the Bay to the Gulf of St. Law- 
rence. The same result would be reached if the old subsequent valley 
were slightly deepened by crustal warping. In either case, with the slow 
uplift of the land, these currents might excavate the channel fast enough 
to keep pace with the elevatory process, thus affording an example of an 
1 Manual of Geology, ed. 4, p. 984. 
