MR MILNE ON THE GEOLOGY OF ROXBURGHSHIRE. 4gg 



other at Dogden Moss, to be, the one a lateral and the other a terminal moraine, 

 he admitted the force of the objections to that theory, founded on the rounded form 

 of the pebbles, and the existence of sand in the heart of the ridges ; but he con- 

 tended, that, in these respects, the moraines in question had been altered by the ac- 

 tion of water, probably derived from the melting of the glaciers themselves ; and 

 he instanced the formation of small ponds in the glacial valleys of Switzerland, 

 along the sides of moraines, in which ponds, layers of sand, and even of small 

 pebbles, are frequently found. But admitting that there may be beds of sand 

 and fine gravel occasionally formed along the sides of moraines, would this ex- 

 plain the existence of such stratified beds in the moraines themselves ? 



Another objection to this theory, and which seems to me equally decisive 

 with the existence of stratified beds in them, is suggested by the character of the 

 rock composing a large portion of the gravel, in these beds. 



In the Liddesdale moraine, many of the pebbles (to the extent of fully 8 per 

 cent.) are granite. If, then, the pebbles have been brought by a glacier descending 

 the valley of the Liddell, and this is the only valley by which a glacier could 

 have flowed past or reached the alleged moraine of Liddell bank, there should be 

 granite rocks in the higher parts of that valley. But, as already mentioned, there 

 is not a trace of granite in those parts, the nearest place where granite exists, be- 

 ing about 25 miles to the west, from which, on account of the levels and character 

 of the country otherwise, no glacier could have reached. 



We must look, then, for some other cause or causes than glaciers, for the 

 transportation of these granite pebbles, and the formation of the knolls and 

 ridges containing them ; and I proceed now to offer the views which have occur- 

 red to me, as to these probable causes. 



(1.) One caiise, by which I believe a very large class of diluvial phenomena 

 may be explained, is aqueous action on pre-existing beds of sand or gravel. 



Assuming the country to have had spread over it, at least in many places, a 

 thick covering of sand and gravel, and which must, as already shewn, have been 

 deposited in a sea standing at a level 1100 or 1200 feet higher than at present, 

 what Avas the effect of the rising of this land to such a height, by which all these 

 sands and gravels became exposed to atmospheric influences ? 



In the first place, the emergence of the land, unless it was gradual, must 

 itself have caused the beds of sand and gravel to be cut up by the force of the 

 retiring waters, in a very remarkable manner. Their action would vary in force 

 and direction according to the nature of the materials and the pre-existing 

 levels. Wherever there was a depression of surface, there the waters would act 

 most powerfully, and thus form deep cuts or gutters in some places, and high 

 ridges in others. Suppose what is now a valley (as that of the Liddell) to 

 have been, when under the sea, filled up with sand and gravel, then, if the 



VOL. XV. PART III. 6 Q 



