NATURAL HISTORY AND PHYSIOGRAPHY OF NEW BRUNSWICK. 447 
to near their mouths in pre-Carboniferous formations, but no doubt, in 
the lower parts of their courses at least, they formerly ran over Car- 
boniferous rocks, the removal of which has let them down upon and 
into the older strata. It is very possible that the most ancient contact 
line of Carboniferous and earlier strata (in the shore line of the Car- 
boniferous seas) occurred at the places where these branches now 
unite and abruptly change their direction, somewhat west of the present 
contact line.* The possibility that some of the Nepisiguit branches 
once formed a part of this system has been considered in an earlier 
note (No. 33.) 
We pass next to consider the north and south v^alley of the North- 
west, which is very remarkable for the way it cuts across nearly at 
right angles to the directions of the western branches. Its true 
morphological head is unquestionably Portage River, from which a 
low portage leads into Gordon or Portage Brook, a branch of the 
Nepisiguit. All these streams (Miramichi, Portage River, Gordon 
Brook and Lower Nepisiguit) are practically nearly in a line, and 
occupy a single great north and south trough or depression with much 
higher ground both east and west ; and the same influences, therefore, 
whatever they were, appear to have determined the Lower Nepisiguit 
and the north and south part of the Miramichi. If now we seek an 
explanation for this great depression, we at once conclude that it can- 
not be a great valley of erosion, but must rather represent a synclinal 
trough due to earth warping. To the eastward the Carboniferous 
rocks rise to a height of over 500 feet above the sea, in consequence, 
as Ells states,! of a great anticlinal uplift represented by “ the high 
ridge that extends eastward from the vicinity of Bartibog station on 
the Intercolonial Railway.” As mentioned in the preceding note, this 
elevation is probably a continuation of the anticline which extends 
through the New Brunswick highlands, and the question arises : How 
originated the depression extending right across this anticline? 
Here, no doubt, the explanation is to be found in a synclinal depression 
parallel with and corresponding to the anticlinal hinge line extending 
from 8t. John to the mouth of the Restigouche, mentioned in the 
preceding note, forming a trough here well marked, and tending to 
* The Carboniferous rocks are here fringed by a narrow band of Lower Carboniferous 
not included within the boundary drawn on the accompanying map, 
. 't Geological Report, 1882, D. 3. 
