National Geographic : 1898 Dec
ATLANTIC COAST TIDES (1) High tide occurs at about the same time from Labrador to Florida, except in the Gulf of Maine, where it is three and a half hours later. (2) A flood-current to southwest appears simultaneously along the whole outer coast preceding high water, which is followed by a general ebb-current to northeast; also appearing simul taneously along the whole coast. (3) Soon after high water outside, which is a time of level within the gulf, a current sets strongly to N. N.W. over the Sill into the Gulf of Maine and the water rises within the gulf. "An impulse observed at one of our current stations is almost im mediately followed by a vertical change on the most distant shore." The current continues to flow thus uphill until high water in the gulf, when it slacks and turns. Three hours later it is flowing out with maximum strength, the gulf is level, and low water is established outside. While the water rises outside and the general flood-current of the coast sets to southwest, the gulf current continues to flow out over the Sill, again uphill, until three hours before high water without, when low water prevails in the gulf. (4) The water bodies move from top to bottom. A diver on the coast of Maine observed distinct motion in 23 fathoms.* Conclusion.-The Gulf of Maine and Bay of Fundy offer a " dead angle " to the general flood-current to southwest, while the ebb-current finds in it " a pocket into which the waters are crowded and, by virtue of their vis viva, piled up in the Bay of Fundy." After comparing with a fluid oscillating in a bent tube with two arms of very unequal size and inclination, the author suggests that the Bay of Fundy tides are a result of a rocking of the ocean into a contracting flume. Mr Mitchell regards the Sill as a node and the oscillations in the Gulf of Maine as produced by the periodic impulse of the North Atlantic oscillation. It is not clear why there is no tend ency toward "pocketing " the flood-current in Cape Cod bay. There also seems to be a difficulty with the period by which the gulf tides follow those of the outer shore. If there is a node on the Sill, and that the only node, the tides without and within should differ in time by six hours. From Mr Mitchell's expla nation of the Gulf of Maine tides, however, he evidently does not mean by node here what is usually meant by the word. * P. 176.