282 L. W. BAILEY ON THE PHYSICAL AND 
Notwithstanding the limitation, however, the effect is so far to set back the stream as 
to produce, except in time of freshet, an alternation of upward and downward currents, | 
accompanied by a corresponding change of level, which is appreciable even at Fredericton, 
a distance of over eighty miles from the mouth, resulting, in low water, in a rise and fall 
of not less than ten inches. From the same cause, combined with the mingling of salt and 
fresh water which accompanies it, the lower portion of the river is less readily frozen, and 
for much shorter periods, than that higher up; while further effects are observable in the 
peculiar distribution of vegetation upon its banks, and the association of fresh, brackish 
and salt-water types in its contained fauna. 
The relation of the falls to the present river-valley being understood, we have in the 
study of the quaternary or post-pliocene deposits, the first indications of a different state of 
things. These are found partly in the relative levels of the terraces, so conspicuous along 
the greater portion of the stream, but especially in that of the Leda-clay, by which these 
are commonly underlaid. From the position of the latter at St. John, and their contained 
fossils, a submergence, in common with that of the New England coast, and amounting here 
to not less than 200 feet, is indicated as having occurred in the so-called Champlain Period ; 
while the extension of similar beds, though without fossils, along a large part of the river 
valley, would appear to show that the same submergence reached far into the interior. 
Under these conditions it is evident thatthe river, as such, could have had no existence, at 
least over the area submerged, and least of all about its present outlet. Had it any pre- 
vious existence ? 
The depth of the Leda-clay at Fredericton, eighty-six miles from the mouth of the 
river, is, as far as has been ascertained, at least eighty feet, or about sixty feet below the 
bed of the present river-channel, indicating therefore a previous erosion to a corresponding 
depth. Again, near St. John, while the river now enters the bay only through the 
narrows and falls already referred to, indications of one if not two former channels of 
discharge, both wider and more direct than the present one, have been clearly recognized, 
and both are now occupied by post-tertiary deposits. The agency of glacial action in the 
widening and deepening of these channels can hardly be doubted, and they may be re- 
garded as marking a third place in the quaternary history of the river valley. That they 
did not altogether originate in such agency remains to be shown. 
The tertiary and secondary formations being without recognizable records in this 
portion of America, except as represented by the triassico—jurassic sandstones, which are 
confined to the coast, we have no direct information as to the condition of the country or 
its drainage during the long interval of time which these formations represent. We do 
know, however, with a good degree of certainty, that during much of that time the land 
stood above the sea-level, and its principal surface-features, due chiefly to the disturbance 
and alteration of palæozoic rocks, having been previously determined, was in the same 
condition as now, as regards the production and distribution of its surface-waters. More- 
over, were it possible to show the existence of any true river-channels in palzeozoic time, 
it would follow that these, unless entirely obliterated by the subsequent removal of their 
bounding formations, would have continued to exist, in some form or other, through all 
the periods which succeeded them. i 
Of the existence of such channels in the carboniferous age proper we have no direct 
proof. The character, however, of the coal-formation, the coarseness of its sediments, and 

