ATLANTIC COAST TIDES 507 



the transmission of the direct impulse across the Georges and 

 Nantucket shoals, nearly 250 miles in an easterly direction. 

 This impulse would be faint and retarded by the long journey 

 across the shoals. Reaching the islands in comparatively open 

 water, the effect will be there to check the falling tide in its de- 

 scent. At Montauk point, however, where the waters are con- 

 fined and the range is small, the eastern tide may overtake the 

 local tide soon after its greatest height and make highest water 

 come later than the local tide would have come. We must think 

 of a massive westward motion of the water here rather than of a 

 progressive wave or in addition to it. The accompanying dia- 

 gram (see p. 506) shows a number of tidal stations with their 

 times and such cotidals as can be drawn 1 h., 2 h., 3 h., and 3 h. 

 45 m. No Mans Land is marked with a heavy cross. 



GULF OF ST LAWRENCE TIDES 



The tidal data for this area are not so numerous as is desir- 

 able. Like the basins described above, the deep connection with 

 the ocean is by a channel much inclined to the direction of ocean 

 movement. Here the axis of the broad entrance trends about 

 northwest-southeast. Impulses across the shelf by the Grand 

 and St Pierre banks must enter the gulf later, and may produce 

 the delay in high water, as before. 



The tides range about four feet in amplitude at the gulf en- 

 trances and swash out flatter in the wide space within. Through- 

 out the deep area between Anticosti, Labrador, and Newfound- 

 land high water is fairly simultaneous, about two hours after the 

 outer coast tide. In the shallower southwest corner of the gulf 

 a tide Avave progresses from the deep channel near Anticosti 

 along the New Brunswick coast to Prince Edward island, on which 

 it divides, passing both north and south of the island and pres- 

 ently meeting tides that come westward from the Cape Breton 

 entrance and the Gut of Canso. Ranges of three or four feet pre- 

 vail save in narrow passages. The meeting of the tides marked 

 on the north and south of Prince Edward island on the charts is 

 a meeting of currents, and in the whole southwest area there is 

 a steady progression not only of the point of high water, but 

 also of the currents. 



All the tide-waves in the southwest rise in 25 minutes' less time 

 than they spend in falling. This is found typical of progressive 

 waves in shallow waters. We call such waves steep fronted and 

 find their extreme case among tides in bores, and in ordinary 



