156 MINERALS AND GEOLOGY 



passed by the accumulation of detrital matters obtained by the waves 

 and breakers of the sea. All who have resided for any length of 

 time on an exposed and rocky coast, must be well aware of the des 

 tructive action of the waves. The cliffs subjected to this action, 

 gradually become undermined and hollowed out; and thus large 

 masses of rock are brought down by their own weight. These, 

 sooner or later, are broken up, and spread in the form of sediment 

 , along the shore, or over the sea-bottom. On some coasts, the 

 amount of land destroyed in this manner almost exceeds belief.* On 

 some parts of the eastern shores of England, and the opposite or 

 western shores of France, for example, the sea has thus carried off, 

 within the present century, from fifty to over two hundred yards of" 

 coast measured backwards from the shore-line along a distance of 

 many miles. Graveyards, shown by maps of no ancient date to have 

 been located at considerable distances from the sea, have become ex- 

 posed upon the cliff-face ; and forts erected by the First Napoleon on 

 the French coast, at two hundred metres and upwards from the edge 

 of the cliff, now lie in ruins on the beach, or have altogether dis- 

 appeared. These localities are mentioned as being more especially 

 known to the writer ; but in all parts of the world examples may be- 

 found of the same destructive process. In the clay and sandy bluffs 

 of our own Lakes, as at Scarboro' Heights on Lake Ontario, and 

 elsewhere, effects of this kind may be equally studied. 



Confining our view at present to these results only, it must be 

 evident to all that an enormous amount of sedimentary matter is 

 annually, or even daily, under process of accumulation. The question 

 then arises as to what becomes of this. The reply is obvious. The 

 detrital matter thus obtained, is deposited in lakes or at river mouths 

 or along the sea-shore, or over the sea-bed contributing day by day 

 to the formation of new rocks. In other words, existing rock 

 masses, worn down by atmospheric agencies, by streams and rivers, 

 and by the action of the sea, supply the material for other and of 

 course newer rock deposits. 



Deposition of Sediments. All sediments diffused through deeper 

 quiet water, arrange themselves under general conditions, in horizontal' 

 or nearly horizontal beds : the latter, if deposited on gently-sloping 



* It would obviously be out of place in an Essay like the present to enlarge on this point. 

 The reader unfamiliar with geological details of this character, should consult, more especially 

 LyelPs Principles of Geology, and also the Cours EUmentaire of the late Alcide d'Orbigny. 



