﻿THE CURRENTS OF THE OCEAN. 129 



by the tide wave upon entering a bay is such, that but a comparatively small part of the 

 body of water brought by the flood impinges upon the point or hook. 



The current is carried towards the bottom and sides of the bay, and loses its velocity 

 by degrees as it meets the resistance of the shores. The cpjiet condition thus produced 

 is the one in which the water drops its burden with facility, and these deposits, to which 

 I have given the name of bay deposits, are very large, speaking always comparatively, 

 and follow strictly the contour of the earlier geological structure. In bays of every 

 dimension there will be more or less conflict of the tidal streams, arising from their ap- 

 proaching each other at last from different sides of the bay. This creates an eddying 

 action, which is also conducive to the increase of the deposit, and may perhaps give it a 

 peculiar outline. Besides the formation at the bottom of every large bay, there will be 

 on the inside of every hook a miniature bay also, in which the same conditions of the 

 tidal current are repeated. 



This bay deposit, then, is generally a skirt of shoal ground, continuous with the 

 beach, and running off some distance under the water, where it is called a bank or shoal. 

 On the inside of the hook, as is seen in the section of Edgartown harbour (Plate II.), 

 the shoal part may be kept quite distinct from the shore by the play of the currents 

 around it, and appear very similar to the isolated ridges formed in the exposed sea. In 

 harbours (which, indeed, are specifically bays) this alluvial structure is never wanting. 

 But in a region of sand the harbours that are found at the bottom of bays owe their 

 existence, in a greater or less degree, to the alluvial deposit. The tidal current after 

 striking the land will follow along its bend, and eddy around any projections that may 

 interrupt its course, depositing a portion of its burden at every tide. The result will be 

 the formation of a hook inclosing a harbour. 



The harbour of Barnstable, at the bottom of the bay of Cape Cod, and the harbour 

 of Nantucket, are both examples of this mode of action. The relation of the small 

 hook to the harbour and its deposits is precisely the same as that of the large hook to the 

 bay. The same forms, proportions, circumstances, and positions of deposit, and the 

 same dependence on the local currents, are observed in each case. 



These little hooks and their appendages are particularly interesting as a study. Liv- 

 ing testimony is frequently obtained concerning their progress, and it is not impossible 

 that an era of hooks may hereafter be added to the eras of dunes and deltas. 

 Beach Point (Plate II.) is a beautiful specimen of the small hook, as Cape Cod itself is 

 of the large hook. These two hooks are perfect in form; Great Point and Sandy 

 Hook, on the other hand, are imperfect, the deposit on the outside being so great in the 

 two last as to prevent the full effect of the eddying in giving the curved shape to the 

 inner point or tongue. 



