OF LOCHABER. 15 



the agitation of the surface of this lake, b)' the various winds 

 to which it may be exposed, will naturally drive its waves 

 against some of the points round its margin, as a a, and will 

 gradually eat away the bank there by the frequency of their 

 action against it ; whilst all being still underneath, it will not 

 be affected any where below. Then, as the water thus mines 

 away the banks, where they are on a level with its surface, the 

 earth and other materials will naturally fall down from above, 

 so as to form two sloping cuts or notches in the side of the 

 hill, as represented by BB, between the dotted and black lines. 

 All the smaller and less ponderous substances, such as gravel, 

 earth, and sand, will of course be washed inwards, towards the 

 deeper part of the lake, and immediately on getting beyond 

 the shallow, will sink down, and form an accumulation at the 

 bottom, and on the sides, as represented in the diagram by D, 

 between the dotted and black lines. But the violence of the 

 waves of a lake, is seldom such as to move those large masses 

 of stone that may be supposed to be uncovered, loosened, or 

 undermined, and brought down by the almost continual, 

 though gentle, fluctuation of its surface towards its shores. 

 These, therefore, would gradually accumulate on its shelving 

 beach. It is almost unnecessary to add, that the breadth of 

 the shelves (BB in the diagram) would vary according to the 

 degree of hardness or softness of the materials forming the va- 

 rious parts of the bank on which the water would have to 

 operate ; and that where stubborn rock should present itself, 

 unless it were placed in some peculiarly exposed situation, it 

 might remain for ages, hardly, if it all affected. Wherever 

 there were swells or promontories, these would in general be 

 most acted upon by the agency of the waves, unless other cir- 

 cumstances should prevent it. This is, indeed, the precise 

 character of all mountain lakes, filing hollows betmeen very 



steep 



