493 





'* 



f 



i 





CHAPTER XX. 



DESTROYING AND TRANSPORTING EFFECTS OF TIDES AND 



CURRENTS. 



DIFFERENCES IN THE RISE OF THE TIDES CAUSES OF CURRENTS — LAGULLAS 



AND GULF CURRENTS — VELOCITY OF CURRENTS — ACTION OF THE SEA ON 



THE BRITISH COAST — SHETLAND ISLANDS — LARGE BLOCKS REMOVED ISLES 



REDUCED TO CLUSTERS OF ROCKS ORKNEY ISLES WASTE OF EAST COAST 



-AND EAST COAST OF ENGLAND WASTE OF THE CLIFFS OF 



HOLDERNESS, NORFOLK, AND SUFFOLK ECCLES CHURCH IN 1839 AND 1862 



SAND-DUNES HOW FAR CHRONOMETERS SILTING UP OF ESTUARIES 



YARMOUTH ESTUARY — SUFFOLK COAST — DUNWICH — ESSEX COAST ESTUARY 



OF SCOTLAND 



OF THE THAMES— GOODWIN SANDS 

 STRAITS OF DOVER — SOUTH COAST 



KENT FORMATION OF THE 



SUSSEX— HANTS DORSET 



PORTLAND— ORIGIN OF THE CHESIL BANK TORBAY — ST. MICHAEL S MOUNT, 



CORNWALL — COAST OF BRITTANY. 





movements of erreat bodies of water, termed 



curr 



their effects cannot be studied separately ; for they produce, 

 by their joint action, aided by that of the waves, those 

 changes which are objects of geological interest. These 

 forces may be viewed in the same manner as we before con- 

 sidered rivers, first, as employed in destroying portions of the 

 solid crust of the earth, and removing them to other places ; 



secondly, as reproductive of new strata. 



Tides.— It would be superfluous at the present day to offer 

 any remarks on the cause of the tides. They are not percep- 

 tible in lakes or in most inland seas ; in the Mediterranean 

 even, deep and extensive as is that sea, they are scarcely sen- 

 sible to ordinary observation, their effects being quite sub- 

 ordinate to those of the winds and currents. In 



some 



Messina 



however, as in the Straits of 



flow to the amount of two feet and upwards ; at Naples and 



at the Euripus, of twelve or thirteen inches ; and at Venice, 



