MR MILNE ON THE GEOLOGY OF ROXBURGHSHIRE. 49] 



(2.) If, however, this was not the case, then it remains to be seen what would 

 be the influences to which the beds and banks of sand and gravel, forming till 

 now the bottom of the sea, would be exposed. 



Here, however, there is a preliminary inquiry necessary. In estimating the 

 eifects of the atmosphere and meteoric agents just adverted to, some considera- 

 tion must first be had of the form and shape of the beds and banks on which they 

 were to operate. Now it may be admitted, that the sand and gravel would in 

 general be spread pretty uniformly over the bottom, though, of course, where sub- 

 marine hollows or valleys existed, the greatest quantity would be deposited there. 

 But whilst this would in general be the case, it is well known that the bottom of 

 the sea, especially where currents prevail, presents in many places narrow banks 

 'with steep sides, and which, according to the course of the currents, are either 

 in straight or in curved lines. 



It is very well known, that all around Great Britain, and particularly along 

 its southern and eastern shores, banks of sand and of gravel (or shingle, as it 

 is sometimes called) are formed by submarine currents. Sir HENRY DE LA 

 BECHE, in his Manual, describes two of these off the coast of Devonshire ; and 

 any one who reads his description of them, cannot fail to be struck with the 

 strong resemblance which they bear, in form, size, and materials, to many of the 

 banks of sand and gravel now existing on the surface of the land. " The sea," to 

 use this author's words, " separates the Chesil Bank from the land for about half 

 its length, so that, for about eight miles, it forms a shingle ridge in the sea. The 

 effects of the waves, however, on either side, are very unequal : on the western 

 side, the propelling and piling influence is very considerable ; while on the east- 

 ern, or that part between the banks and the mainland, it is of trifling import- 

 ance." Unfortunately, neither the height of this ridge or bank above the bottom 

 of the sea, nor the slope of its sides, is given. But if the woodcut in illustration 

 of the description be correct, the sectional dimensions and shape accord com- 

 pletely with those of the Roxburghshire and Berwickshire kaims. 



The other case described by the same author, is known as the Slapton Sands. 

 Sir HENRY describes these as composing, " at the bottom of Start Bay, and for 

 the distance of about five or six miles, a considerable bank, principally composed of 

 small quartz pebbles." " This bank," the author adds, " protects and blocks up 

 the mouths of five valleys ;" so that we have here what AGASSIZ would describe 

 as a terminal moraine, extending across the vomitaries of five glacial valleys. Sir 

 HENRY mentions, that, in November 1824, a breach was made by the sea, through 

 this protective barrier, and that it " continued open for nearly a year, becoming 

 gradually smaller. The complete restoration of the sands," he adds, " was has- 

 tened by throwing a few bags filled with shingles into the gap, upon which two 

 or three gales soon piled up a heavy beach." The upper portion of this bank 

 is described as being in some places above the level of the sea ; for Sir HENRY 

 observes, that " the old bank (that is, I suppose, before the breach was made in 



