506 



ATLANTIC COAST TIDES 



with tidal stations on either hand and even on islands out in the 

 channel. This entrance to the sound has a depth of 30 fathoms. 

 The deep axis of the sound lies near the southern shore in 15 to 

 20 fathoms, with a constant gentle rise to the north. The main 

 water body clearly oscillates en masse. This is evident from the 

 synchronism of tides throughout the sound. It seems equally 

 clear that the impulse comes from the outer coast as a progres- 

 sive wave, perhaps combined with a massive movement, which 

 consumes two hours in advancing through the 10-mile entrance. 

 In this reach of slow progression the ranges are naturally slight, 

 and there is little gain, but the narrowing and shoaling of the 

 western end of the sound causes the tide to augment its range 



TIDAL HOURS 



From NoMonsLand 

 i 



LONG ISLAND SOUND 



rapidly in that direction from 2 to 7.2 feet. This is accompanied 

 by a gentle steepening of the wave front, and is the natural re- 

 sult of bodily fluming the water into a narrow, shallow bay 

 head, whatever the driving force, as we shall see presently. 



For the times it is striking that from No Mans Land to Block 

 island there should be a difference of but 11 minutes, while the 

 far shorter distance to Montauk point consumes three-quarters 

 of an hour. Some light may be had by referring again to the 

 east-west line of the oceanic oscillation. The nearest deep water 

 to Montauk point, Block island, and No Mans Land is some 70 

 miles to the south. From this point, though at right angles to 

 the direct line of the motion, the earliest tidal impulse would 

 probably arrive, and the indications of early time at No Mans 

 Land and Block island result. This would not, however, prevent 



