504 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 bj r 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 Ba}' 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 Ba}' 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. 



