RELATION TO HARBORS 1/3 



which case a e^ood deal of upward and downward move- 

 ment at either end of the section ma)' take place without any 

 alteration in the position of the shore-line, or the pivotal 

 point may be some distance within the land, in which case 

 the movement may lead to a gain of the sea upon the con- 

 tinent. In the third possible condition the point of no motion 

 may be seaward of the shore, when, though the nature of the 

 movement may be exactly the same as before, the coast-line 

 will rise and the land gain upon the sea. 



In the way above suggested we may account for the 

 frequent changes in the direction of the movement which 

 occurs in those parts of a continent which are near the shore- 

 line, without having to suppose that the whole mass of the 

 continent undero-oes like changes of level. The inland dis- 

 tricts may be in a somewhat constant manner rising into the 

 air, while the coast-line, ownng to slight accidental changes in 

 the position of the fulcrum points, may be subjected to con- 

 stant oscillations of movement. 



If the sea-shore remains in the same position for a long 

 time, the ordinary effect of the coast-line actions is to close 

 the harbors, either through the accumulation of debris brought 

 into them by the streams or by the sands which the waves and 

 coastal currents are continually impelling into all the recesses 

 of the shore. Where such conditions occur we may reason- 

 ably expect to find a coast to a great extent destitute of 

 harbors, though we may trace the evidence of their former 

 existence by noting the basins filled with alluvium which 

 exist along the margin of the land. 



Where any coastal region is without considerable rivers, 

 and where there are no conditions such as we have hereafter 

 to describe which lead to the formation of indentations, 



