NATURAL CHANGE OF COAST-LINE. 38D 



There are also cases wliere sunilar apparent effects are produced 

 by local oceanic cm-rents, by river deposit or erosion, by tidal ac- 

 tion, or by the influence of the wind, upon the waves and the 

 sands of the sea-beach. A regular current may drift suspended 

 earth and seaweed along a coast until they are caught by an eddy 

 and finally deposited out of the reach of further disturbance, or 

 it may scoop out the bed of the sea and undermine promontories 

 and headlands ; a powerful river, as the wind changes the direc- 

 tion of its flow at its outlet, may wash away shores and sand-banks 

 at one point to deposit their material at another ; the tide or 

 waves, stirred to unusual depths by the wind, may gradually wear 

 down the hue of coast, or they may form shoals and coast-dunes 

 by depositing the sand they have rolled up from the bottom of 

 the ocean. These latter modes of action are slow in producing 

 effects sufficiently important to be noticed in general geography, 

 or even to be visible in the representations of coast-line laid down 

 in ordinary maps ; but they nevertheless form conspicuous fea- 

 tures in local topography, and they are attended with conse- 

 quences of great moment to the material and the moral interests of 

 men. The forces which produce these limited results are all in a 

 considerable degree subject to control, or rather to direction and 

 resistance, by human power, and it is in guiding, combating and 

 compensating them that man has achieved some of his most 

 remarkable and most honorable conquests over nature. The 

 triumphs in question, or what we generally call harbor and coast 

 improvements, whether we estimate their value by the money 

 and labor expended upon them, or by then* bearing upon the in- 

 strengthened the effects, whatever they may be, of thickening the crust of the 

 earth in the Bay of Bengal. In such cases, then, human action must rank 

 among geological influences. See Stoppani, Corso di Geologia, i. , p. 268. 



To the geological effects of Ihe thickening of the earth's crust in the Bay of 

 Bengal, are to be added those of thinning it on the highlands where the Ganges 

 rises. The same action may, as a learned friend suggests to me, even have a 

 cosmical influence. The great rivers of the earth, taken as a whole, transport 

 sediment from the polar regions in an equatorial direction, and hence tend to 

 increase the equatorial diameter, and at the same time, by their inequality of 

 action, to a continual displacement of the centre of gravity, of the earth. The 

 motion of the globe, and of all bodies affected by its attraction, is modified by 

 every change of its form, and in this case we are not authorized to say that 

 such effects are in any way compensated. 



