298 RECORDS OF POST-TRIASSIG CHANGES 
heading back to a low divide some three or four miles from the 
coast. 
During the submergence of the region in late Mesozoie or 
early Tertiary times, the streams were drowned by the sea and 
the silicious and caleareous deposits described were laid down in 
the old river valleys. Deposits forming in this way would be 
protected from the disturbances of the open shore, and probably 
be composed of fine sediment laid bare at each low tide and dried 
and sun cracked in bright warm days until carried below the 
tidal limts by the slow subsidence of the whole region. The 
limestone deposits indicate a submergence great enough to have 
formed large inland basins in the broad valleys in the sandstone 
country south-east of the edge of the trap sheet. These were pos- 
sibly separated from each other by low divides which would be 
gradually lessened by the rapid vertical decay of this rock refer- 
red to earlier in this paper. When once covered by the sea, the 
swiftly moving north-east and south-west tidal currents char- 
acteristic of this region would scour out the valley at a rapid 
rate, while the trap sheet would not retreat along its edges at a 
corresponding rate since the frost work had not yet been 
inaugurated, mild and warm climates extending at this time 
even within the Arctic Circle. On the re-elevation of the country 
in middle or late Tertiary times, the rivers would not return to 
their ancient channels across the trap which were now higher 
than the valley floor and filled in with deposits of the kind 
described, but would flow along the valley parallel with the 
mountain in either direction only discharging at the lowest out- 
lets as Digby Gut at the south-west and Minas Basin and Channel 
at the north-east. 
The colder climates of late Tertiary times were now setting 
in with winter frosts and snow, and the sheet of trap would 
begin the rapid horizontal retreat which has continued until the 
present day. 
Boulder Clay. 
Boulder clay containing many striated stones from local 
sources occurs throughout this whole region and is seldom absent 
