ATLANTIC ESTUARINE TIDES 



401 



rias of northwestern Spain, tidal rivers emptying into tidal Lays, 

 both resulting from the drowning of older river valleys in the 

 sea. The simple type is a valley cut in rocks of uniform texture, 

 and flares uniformly toward the sea. 



While the Delaware furnishes a good illustration of the com- 

 bined tj'pe, the Chesapeake affords an exception of almost equal 

 interest. 



The following table summarizes the facts for the Delaware : 



DELAWARE TIDES 







I 



II 



III 



IV 



V 



VI 



■yn 



VIII 



IX 



H. W. interval from capes. 







4.6 



23 

 .6.0 



16 



6.2 



11 

 6.3 



14 



0.2 



15 

 6.1 



11 

 5.4 



10 

 5.6 



7 

 5.1 



13 

 4.1 



H. W. advance in last hour 



(miles). 

 Mean tide range (feet). 



h. m. 

 6 2j 



h. m. 

 5 43 



h. m. 

 5 37 



/(. m 

 5 25 



h. m. 

 5 25 



h. m. 

 5 19 



h. m. 



5 7 



h. m. 

 4 49 



h. m. 

 4 43 



h. 7)1. 

 3 55 



Duration of rise. 



6 



6 42 



6 48 



7 



7 



7 & 



7 18 



7 36 



7 42 



8 30 



Duration of fall. 



The dotted lines on the map represent the positions of the pro- 

 gressing wave-front at successive even hours after it passes the 

 capes. They are numbered with Roman numerals to the right, 



THE DELAWARE 



the feet of range being also given in Arabic numerals. T = 

 Trenton, P = Philadelphia, and the dots in the lower bay repre- 

 sent observation stations on shoals that enable us to ascertain 

 the convexity of the advancing wave-front. From the table, and 

 still more from the map, it appears that for the first three hours 

 the tide advances with decreasing speed — 23 miles the first hour, 



