224 



ON TIDES AND TIDAL ACTION IN HARBORS. 



light, ill a direct line with the swash channel, which is the second open- 

 iug_showu on the sketch — above the Hook ; the shoal lying between 

 the main or Hook channel and the swash channel being known as 

 Flynn's Knoll. The greatest depth over the bar is twenty-two feet at 

 mean low water ; and very nearly the same depth can now be carried 

 through the swash channel, which formerly was three feet shallower, 



ENTRANCE TO NEW YORK HARBOR 



but has deepened since the cross-section between the Hook and Flynn's 

 Knoll has been diminished by one-third its area by the growth of the 

 Hook. This relative change in the capacity of the channels has not, 

 however, affected the depth on the outer bar, which, according to the 

 principles above laid down, is dependent mainly upon the area of the 

 tidal basin within. 



The depth of twenty-two feet at mean low water, which is now main- 

 tained at the entrance through the sands constantly thrown up by the 



