National Geographic : 1898 Sep
ATLANTIC ESTUARINE TIDES ST JOHN RIVER TIDES Our data here are all for mean springs of July and August, being due to a study by A. Willmer Duff.* In putting these data into the usual form, the time intervals have been taken from Indiantown. Although the tides are of a good river type, there is a unique feature in the tidal falls at the river's mouth. The entrance to the Bay of Fundy at the city of St John is by an estuary five miles wide in deep water. Spring-tide ranges at the cityareof27feet; timeofrise,5h.40m.; fall,6h.45m. Back of the city ' the waters of the river, previously occupying a channel remarkable for its extent and breadth, become abruptly confined in a narrow gorge [which] 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 harbor and river and the known rise of the tide, 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. 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 down ward currents, accompanied by a corresponding change of level, which is appreciable even at Fredericton, a distance of over 80 miles from the mouth, resulting at low water, in a rise and fall of not less than 10 inches." t Four times in the twenty-four hours there are ten-minute periods of level water,+ and then steamboats can safely pass.l At very high freshets in April and May there is no inward fall, as the tide does not rise high enough.|I There has been some discussion as to the propriety of calling the oscillations that result in the St John river tides. Mr Duff's investigation, however, seems decisive. The oscillations are tidal in shape, period, and progression, and are visibly born of the Fundy tides in the Narrows; they are therefore tides. The distances in the table accompanying are from Indiantown, just upstream from the Narrows ; the ranges in inches. * Bulletin of Nat. Hist. of New Brunswick, vol. xv, 1897. t L. W . Bailey, Roy. Soc. Can. Trans. 1882, p. 281. $ J. W. Bailey, St John River, p. 135. SWard's Account of the River St John, p. 17. || Lockwood's Nova Scotia, p. 97.