1 86 SEA AND LAND 



These harbors are (generally shallow and are not comi:)letely 

 landlocked. Inasmuch as they lie amid drifting sands they 

 are likely to be rapidly shallowed unless carefully guarded 

 from the invasion of sediment by engineering skill. Although 

 these inlets, as compared with those produced by other agents, 

 are of relatively little size and not well suited to afford shelter 

 for ships, they occur on parts of the coast which are otherwise 

 without havens, and on this account have a considerable eco- 

 nomic importance. 



Besides the morainal deposits, the glacial sheet left upon 

 the country which it had occupied a vast amount of drift 

 materials disposed in an irregular manner, so that the result- 

 ing surface of the earth consisted of innumerable ridges and 

 valleys. At the close of the ice period the sea, penetrating 

 into the depressions of the surface, formed innumerable shal- 

 low bays. The greater portion of these has been filled with 

 sediments or closed by the growth of marine marsh deposits. 

 Here and there, however, they still afford shallow harbors, in 

 most cases suitable only for small vessels engaged in shipping 

 or in coastwise traffic. Wareham and Chatham harbors on 

 the southern coast of Massachusetts are good instances of 

 this peculiar variety of havens. Farther north on this con- 

 tinent and in the glaciated districts of Europe about the North 

 Sea, inlets of this nature are of common occurrence, but as 

 they lie in districts provided with shelters for ships by other 

 and more effective haven-making agents, they have little 

 value to mariners. 



