OF THE EARN AND TEITH. 169 



submarine banks belonging to the time when Scotland was submerged, but 

 this seems disproved by the fact, that wherever such submarine banks occur, 

 they swarm with all kinds of marine life, while in regard to any trace of such 

 life, these kames are invariably an utter blank. But, indeed, similar difficulties 

 attend all the theories hitherto suggested. Nor ought this to surprise us. 

 We do not know what it is for a country once incased in ice as Greenland 

 now is, to have the ice-sheet lifted off or melted from the face of hill and plain. 

 Into what forms the subjacent materials of gravel and sand would be thrown — 

 what would be the modes of operation of the forces let loose, it is difficult to 

 conjecture. No example of such a process has been witnessed, and yet it is 

 certain that Scotland passed through it. It is little wonder if among its results 

 there should be some residual phenomena for which it is difficult to account. 

 Among these it would seem we must place the kames or escars, and the gravel 

 mounds associated with them. At all events, their position appears to lie 

 between the period of arctic climate and the time of that series of terraces 

 which this paper describes, and which were, it is probable, built up out of the 

 materials furnished by these pre-existing gravel deposits. 



In deciding the geological position of the terraces, however, we must not 

 forget the fossils of the peat and the associated carse clays referred to at the 

 beginning of this paper. For several miles above Bridge of Earn these remains 

 occur in abundance, but evidently they have been drifted from some distance, 

 brought down by the current, and they show what the flora of Stathearn had 

 been at the time when the peat and carse clay were deposited. In regard to 

 the extension of the carse clay itself, it can be traced up as far as Kinkell, 

 where its grey colour and fine unlaminated structure were quite distinct/"" form- 

 ing part of terrace c, as shown in sketch 7. Above Kinkell, the same terrace runs 

 on, but the place of the clay is taken to a great extent by sands and gravels, 

 and these materials get on the whole coarser the further you go up the stream. 

 All this is easily explained. The coarser the material, the less easily is it 

 moved forward by the current, while clay in the form of mud is floated to the 

 furthest distance. The highest terrace, therefore, which consists at first of 

 gravel and sand, with a little clay, presents through all the lower reaches of the 

 river little else than large sections of the finest carse clay. These carse clays, 

 and the underlying peat near Bridge of Earn, form, as we have seen, properly 

 only one deposit, and the result would seem to be that these fossil leaves and 

 hazel nuts, &c, give us the flora which grew along the valley at the time when 

 the oldest of these terraces were formed.t 



* See Fig 1, PL iv. 



' There seems good ground for holding that the peat heds of the Earn belong to the time when 

 the land stood comparatively high. But when Mr Jamieson makes the land again sink, and brings 

 in the sea in order to deposit the estuarine mud of the carse, not only does the fossil evidence go 

 against this, but there is the decisive fact already pointed out, that the peat and the carse clay are so 



VOL. XXVI. PART I. 2 Y 



