402 



ATLANTIC ESTUARINE TIDES 



16 miles the second, and 11 miles the third. During the same 

 period the mean tidal range is increasing from 4.6 feet to 6.3 feet. 

 These two characters are taken to define the bay type of tides : 



(1) Progressive loss of speed j the b 



(2) Increase of tidal range - 1 ' 



Above Delaware City there is observed a steady falling off in the 

 range. The rate of progress is here somewhat irregular. These 

 two characters define the river type of tide : 



(1) Irregular advance, commonly 10 or 12 miles per hour. 



(2) Decrease of tidal range. 



The last two lines in the table indicate a feature common to both 

 types — the steepening of the front of the advancing wave, man- 

 ifested in the times by quicker rise and slower fall. Outside of 

 the estuaries, all along our Atlantic coast the times of rise and 

 fall are equal. While bay and river together go to make up the 

 geographic estuary, it may happen that one of the parts is miss- 

 ing, as with the Kennebec, which enters the sea by a narrow 

 fiord and has no bay, or the Penobscot, shown by its tides to be 

 wholly of the bay type. The Connecticut river has a sort of bay, 

 but so choked with sediments as to be tidally inefficient. The 

 Hudson enters the side of Raritan bay, both being good types of 

 their kind, but not parts of one geographic whole. Chesapeake 

 waters are anomalous. 



The following are the ranges of the best illustrations in the area: 





Bay. 



River. 





11' to 14' 



14' to 0.9' 



St John 



26" to 6" 





9' to 13' 







8.3' to 4.3' 







3.0' to 0.8' 







4.0' to 2.3' 





4.0' to 5.4' 

 4.0' to 6.3' 







6.3' to 4.1' 







CHESAPEAKE TIDES 



The Chesapeake is a drowned river valley into which drowned 

 branch valleys pour abundant waters. Deep water is found 

 within, yet the communication with the ocean is narrow and shal- 



