ATLANTIC COAST TIDES 499 



it is difficult to decide in what direction the cross-section should 

 be drawn, but in general an east-west line gives satisfactory re- 

 sults, besides according well with the general conception of the 

 Atlantic tidal oscillation. But it is certain that the tidal im- 

 pulse is not limited closely to transmission in one direction. 

 The tidal range appears to vaiy with the width of the continental 

 shelf where the descent to the sea is unbroken; where shoals 

 stand on the shelf margin the range is thereby diminished, being 

 greatest opposite the openings between the shoals. 



The general tide relations on the coast are as follows : 



In the north, in the Nova Scotia-Newfoundland area, the line 

 of 100 fathoms is about 200 miles offshore, if measured on an 

 east-west line. A series of banks lies just within this line, while 

 close without the descent is rapid to 2,000 fathoms. The tide- 

 ranges are from A.\ to 7 feet. 



In the Middle bay, from Nantucket to Hatteras, 100 fathoms 

 and the descent to oceanic depths are alike some 70 miles out. 

 Tides range from 2 to 4 feet. 



In the Southern bay the 100-fathom line is 30 to 80 miles from 

 land, while the descent to 2,000 fathoms lies 240 miles out. 

 Tide-ranges are here from 4 to 8 feet. 



THE NORTHERN AREA 



The tide reaches shore first at Countr}' harbor, well up toward 

 the Gut of Canso, and due west from the dee}) entrance to the 

 Gulf of St Lawrence. Thirty minutes later it has reached the 

 southwest end of Nova Scotia and the northeast end of Cape 

 Breton island. After another half hour it reaches the south 

 coast of Newfoundland. ' 



The tidal impulse seems to enter these waters b}^ the entrance 

 to the St Lawrence, the Banks of Newfoundland barring off the 

 ocean to the east. If this be true, it is here transmitted along 

 a southeast-northwest line. That this is so is confirmed by the 

 fact that the tide reaches the south side of Sable island an hour 

 before it appears on the north side. Sable island stands close 

 to the eastern margin of the shelf, southeast from Country har- 

 bor. The smaller ranges occur on the south coast of Newfound- 

 land, where the tide has only indirect access to shore. 



MIDDLE BAY TIDES 



The Middle bay lies in a 120° angle of the coast, with vertex 

 at Sandy Hook and the sides resting on Nantucket and Hatteras 



