ABSTRACTS 1882-83.

I.-On the Physical and Geological History of the St. John River, New Brunswick.

By L. W. BAILEY, M.A., Ph. D.

(Read May 26, 1882.)

The main purpose of this paper was to call attention to a few facts connected with the physical and geological structure of the St. John-River valle y, as bearing upon its origin and history; and especially as helping to show, what has been hitherto recognized in but few instances, that not only do our larger rivers, more particularly in the older portions of the continent, owe their present features to causes often of very remote origin, but that they were themselves in existence, in part at least, at very early periods.

Referring first to its present aspect, the course of the St. John in relation to the physical features of the region traversed, was pointed out as necessarily determined by conditions different from those which now exist; that course, for some three hundred miles of its length, taking place apparently irrespectively of the present irregularities of surface; being at right angles, or nearly so, to the present feature-lines of the country, and intersecting, in the distance named, not less than five great axes of elevation, and at least eight distinct geological formations. In three if not four instances these axes still afford sufficient resistance to produce more or less considerable falls, viz.: Little Falls, Grand Falls (100-150 feet), Meductic Falls, now artificially reduced to rapids, and the falls beneath the suspension-bridge at the mouth of the river. It is in connection with these falls and the transverse gorges which accompany them, that we meet with the most interesting facts illustrative of the river's history.

In the case of the falls at the outlet, long known, from its relations to the tides of the Bay of Fundy, as constituting a unique feature in the structure of the river, the facts observed are especially important. Produced where the waters of the river, previously occupying a channel remarkable for its extent and depth, become abruptly confined to a narrow gorge, this fall has its immediate origin in a band of pre-Cambrian rock crossing the stream, obliquely and forming a barrier, over which the waters of the river and of the bay flow alternately. From the relative levels of the harbour and river, and the known rise of the tide, the latter (varying from twenty-five to twenty-seven feet), it would appear that the inward fall over the barrier at the suspension bridge is from nine to ten feet; but as this inward fall is wholly confined to the last third of the flood-tide, attaining its maximum with the latter, and again rapidly receding, the interval during which the river is effectively resisted is greatly limited, not exceeding three or four hours out of every twelve.

Sec. IV., 1882-83 36.

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 that the 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 previous 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 regarded 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 paleozoic rocks, having been previously determined, was in the same condition as now, as regards the production and distribution of its surface-waters. Moreover, were it possible to show the existence of any true river-channels in palæozoic 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.

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

the entire absence of marine fossils, sufficiently attest the operation of fresh waters at that time, as well as the general rapidity and wide distribution of the currents by which its area was traversed. In the lower-carboniferous and Devonian ages we have what would seem to be more positive proofs of the existence of such channels at very early periods.

The first of these evidences is to be found about twelve miles above the city of Freder icton, where the stream, after intersecting the great central granitic axis, sweeps in the form of a broad crescentic curve across the highly disturbed Lower Silurian slates which flank this axis on the southern side, producing a trough, a mile or more in length, of no great width, and bordered for most of its length by perpendicular bluffs, on one side, at least, a hundred feet or more in height. While these bluffs are composed of nearly vertical strata, and consist chiefly of very hard quartzose rocks, there may be seen at their base, in direct contact with, and, as it were, plastered against their cut edges, a series of beds of wholly different character. They are horizontal, or nearly so, and in colour, as well as in other features, are readily recognizable as a portion of the lower-carboniferous formation, so largely displayed around the border of the coal-basin only a short distance south. From the position and relation of these beds the inference was drawn that the gorge described must have been in existence in the lower-carboniferous period, and as it was then partly filled and obliterated by the marine sediments of the period, it must have owed its origin to some earlier era of emergence and hence to some fresh-water stream, of which this portion at least coincided with the modern river.

That the period in question was that of the later Devonian is regarded as probable, both from the relations of the beds of this era to those of the lower-carboniferous, indicating that the principal surface-features of the region had been determined prior to the latter, and also, from the character and distribution of the Devonian fossils, proving the existence of a wide-spread terrestrial flora. In one instance, at least, the mode of occurrence of the latter is such as to point directly to the existence of considerable fresh-water streams at the time of their accumulation.

The case in point, first noticed by Mr. G. F. Matthew, is found in the peculiar features presented by the Devonian rocks of the Lepreau basin, about twenty miles westward of St. John, where the coarse and irregularly-bedded sandstones which there make up the bulk of this formation are remarkable for containing large trunks of fossil trees (Dadoxylon), now largely anthracised, in such numbers and at such positions as to indicate that they were drifted logs, brought down by some large stream during a period of flood, and imbedded in the sand bars about its mouth. Where this stream had its source, and whether or not it was in any portion of its course coincident with the present valley of the St. John, may be a matter of conjecture. It may, however, when taken in connection with the facts already stated, be fairly regarded as affording proof of the existence of a distinct drainagesystem in this portion of New Brunswick at least as early as the latter part of the Devonian era.

As to periods earlier than the Devonian, the comparatively limited extend of dry land, the paucity of hill-ranges, and the general prevalence of marine conditions, were all unfavorable to the development of river-systems, and there is no reason to suppose that this part of North America differed materially from others in this respect. Indeed the abundance of marine fossils met with along large portions of the district traversed by the St. John, both of Upper and Lower Silurian age, sufficiently attest this fact. The influence of these more

remote ages upon the present aspect of the river has probably been only an indirect one, by contributing to the causes which subsequently determined the nature and direction of its flow. Among the effects which can with probability be referred to such early-acting causes, may be especially mentioned the parallel lake-like troughs which mark its southern course, such as those of the Long Reach, the Belleisle and the Kennebecasis, the latter thirty miles or more in length, and having in places a depth of over 200 feet. The fact that these are in each case excavated out of primordial strata, in valleys bordered by hard Huronian rocks, and that these valleys have been deeply filled by lower-carboniferous sediments, only to be again carved out to their present form and depth, bear striking testimony to the antiquity as well as to the varied phases of the river's history.

II.-On Some Ferruginous Concretions, from the Bed of Grand Lake, Nova Scotia.

By THE REV. D. HONEYMAN, D.C.L.

(Read May 25, 1882.)

The author's attention was first called to these curious concretions some three years ago by a resident of the vicinity, who brought one of them to the Halifax Museum, stating that it was one of many, of various shapes and sizes, which could be seen lying on the bottom of the lake. Subsequently a number of specimens were secured. They all have an irregularly shaped mass of slate or sandstone for their centre or bottom, around which the ferruginous matter has been deposited in concentric lines. The outline of the stone, which is always exposed on the upper and under sides, appears, to some extent, to have determined the more or less circular form of the concretion. They occur both in flat and in saucer-shaped forms, the latter having a depth up to one and two-tenths of an inch. The largest specimens hitherto found do not exceed six inches in their larger diameter.

A partial analysis showed the concentric layers, which present a granular structure, and are exceedingly friable, to consist of hydrous peroxide of iron, with traces of manganese. It would thus appear that a deposit of manganiferous bog iron-ore is now in process of formation over portions of the bed of Grand Lake.

I cannot at present offer any satisfactory explanation of the causes which have determined the peculiar saucer-shaped form of many of these interesting concretions, and which led some persons to imagine they were specimens of Indian pottery.

I have much pleasure in presenting the specimen now exhibited to the Dominion Geological and Natural History Museum.

III.-On Erosion from Coast-Ice and Floating Ice in the Baie des Chaleurs.

By R. CHALMERS.

(Communicated by Dr. J. W. Dawson, May 25, 1883.)

Mr. Chalmers describes the outcrops of the paleozoic rocks along the south side of the Baie des Chaleurs, as presenting a somewhat flat and even surface, not ordinarily marked with glacial striæ, up to a height of fifty to seventy-five feet above the sea-level. A similar appearance is presented by the beds below the sea-level along the coast. He connects this with the action of the floating ice, now very evident in the bay. In winter, a fixed border of ice is formed along the coast, from two to six feet thick, and extending for a distance of