508 ATLANTIC COAST TIDES 



short waves in the surf of the beach, with quick straight uprise 

 of water in front and long gentle slope behind. In the north- 

 east, as in the shelf waters generally, rise and fall are of equal 

 duration. 



BAY OF FUNDY TIDES 



A brief note follows on a region geographically intermediate 

 between the estuaries and the shelf basins. 



These are of a special character, as was implied in the discus- 

 sion of the Gulf of Maine. It is not a typical estuary. The fact 

 that its area is almost coextensive with the soft Triassic sand- 

 stones that appear in patches all about its shores, together with 

 the fact that it is now rapidly cutting these remnants away, is 

 perfectly compatible with the former existence of Triassic rocks 

 through most of the area with an axial valley, narrower and 

 more typical in form, through which the Petitcodiac, St John, 

 and St Croix poured their waters into the Gulf of Maine. Given 

 such conditions, the rushing tides resulting from the massive 

 oscillation of the gulf waters into the estuary must have tended 

 toward the present conditions.* 



A good description of the Fundy tides is still lacking. The 

 greatest mean range is of 43.5 feet in the Basin of Minas, 50 feet 

 at mean springs. Favoring meteorological conditions may in- 

 crease this by nearly one-half on rare occasions, so that a 70-foot 

 tide is not incredible. It is found that narrowing bays multiply 

 an accidental or non-lunar disturbance of water level in the same 

 proportion that they do the tidal oscillation. Thus Geneva is 

 situated at the head of a narrowing shoaling arm of the Lake of 

 Geoeva, perfectly comparable to the Bay of Fundy, with but a 

 sixteenth the water volume of the whole lake. The seiches or 

 swaying oscillations of the whole lake produce a wave two or 

 three times as great at Geneva as at points anywhere in the main 

 lake, for large oscillations or for small. t 



Similarly, barometric disturbances over the Gulf of St Law- 

 rence that cause only a slight change in the small local tide add 

 six or seven feet to the 17-foot Quebec tide.t During a storm 

 which raged in Chesapeake bay in September, 1876, the water 

 rose four feet two inches above mean high-tide level at Alexan- 



* Similarly Delaware bay is believed to have been widened by the tide, though long- 

 shore action in the shallows outside is continuously striving to dam it off from the sea. 

 tForel, Le Leiman, vol. ii, Seiches. 

 J 30 Jan., 189 1, and 8 Feb., 1895. W. Bell. Dawson, Royal Soc. Can.,51895, vol. i, p. 26. 



