1874-75-] IQ 5 



have been deposited in water, and that it must have required a 

 long period to form them. But the question remains still to be 

 answered, how were these materials formed into ridges or hills ? 

 Water distributes the materials which it holds in suspension evenly 

 along the surface over which it spreads, but it has no power to 

 heap up this matter into hills. After much consideration I have 

 come to the conclusion that the following series of events must 

 have taken place since the Glacial period in the districts to which 

 I have referred. You will please excuse me if, for the sake of 

 clearness, I recapitulate something of what has been already said. 



(i.) Towards the close of the Glacial period the land sank, and the 

 lower grounds were for a long period covered by the sea. This sea 

 swept away much of the Glacial drift, and formed, by water-rolling 

 large quantities of sand and pebbles, which were distributed evenly 

 along the sea bottom. 



Much confusion of thought has been occasioned by the officers 

 of the Geological Survey, and writers on geology generally, using 

 the term "drift" to indicate both stratified and unstratified de- 

 posits. Now the unstratified accumulations of boulders and clay, 

 to which, I think, the term " Glacial Drift " should be restricted, 

 are mainly, as I have stated, confined to the higher grounds, the 

 low lands being generally covered with water-rolled stratified sands, 

 gravels, or clay beds. Where glacial drift occurs at low levels, as 

 at Castle Espie quarries, or the sandstone quarries near Dundon- 

 ald, it is of an unusually tenacious nature, and consequently 

 was able to resist denudation. So distinct is the line of demarca- 

 tion between the ice-formed and the water-formed deposits, that 

 I have often been able to trace on the slope of a hill the exact line 

 to which the water had risen after the submergence of the land. 



The islands in this Post-Glacial sea are, I think, represented by 

 the hills at present covered with undisturbed drift, as well as those 

 higher ridges from which the drift has since been removed by 

 atmospheric denudation. 



I may here observe, that the land was covered with sea water, 

 not fresh water, inasmuch as marine shells have been found in the 



