The Scottish Natwalist. 7 



few sporadic stones. Perhaps these may have been carried down 

 by shore-ice, or even by ground-ice. With the possible exception 

 of these scattered stones, we have no other evidence of the former 

 presence of floating-ice. But the generally unfossiliferous char- 

 acter of the brick-clays is quite in keeping with the view that 

 the estuary of the Tay was fed by large muddy rivers, flowing 

 from glacier-valleys — such as the Tay, the Isla, the Almond, the 

 Earn, and others. We can understand how, under such condi- 

 tions, the upper waters of the estuary would be unfavourable to 

 life, and how shore-ice, and even ground-ice, might now and again 

 freeze up and transport gravel-stones and shingle. 



At a subsequent period, when the sea had retreated to its 

 present level, the Tay cut its way into the deposits of the second 

 terrace, and gradually formed that succession of alluvial plains 

 which are now seen skirting the river at various heights, from 

 twenty feet or so down to a yard or less above its bed. 



