154 REV. THOMAS BROWN ON THE OLD RIVER TERRACES 



sufficient, I believe, to show the general course of these deposits. Their outline 

 on the side furthest from the river is not attempted. 



Having thus examined the Earn, it seemed desirable to test these views in 

 some different district ; and next summer (1867), accordingly, I went to 

 Callander, on the banks of the Teith, the chief stream in the basin of the Forth. 

 From the details about to be given it will be seen that the same terrace system 

 is developed along the Teith, if possible, more strikingly than I had seen it 

 on the Earn. Other occupations made it impossible for me at once to follow 

 up the subject, but, having during last autumn verified the leading points, I 

 shall now endeavour to state the results. 



Origin of the Terraces. 



The great point of interest is the question as to how these terraces were 

 formed, and I go into the discussion of this the more willingly, because it will 

 lead me to describe the way in which these deposits occur, and will show their 

 continuity along the different valleys. 



One explanation ascribes their formation to the sea at a time when the 

 land was to a great extent submerged, and when our river courses were fiords. 

 These terraces, it is said, are the old shores, against which the tides rose and 

 fell. Great prominence has been given to this view by various writers, and 

 especially by Dr Robert Chambers in his work on " Ancient Sea Margins," 

 part of which refers to the Tay and its tributaries."" There is one difficulty, 

 however, in the way of this opinion, from the utter absence of marine fossils. 

 Even where the most delicate leaves of land plants are beautifully preserved we 

 can find no trace of the sea. Another difficulty lies in the impossibility of con- 

 ceiving how the threefold terrace system could have been formed by marine 

 action. The sea can lay down only one line of beach at a time. Take the 

 valley, sloping upwards for 240 feet from Bridge of Earn to the foot of Glen- 

 artney, — suppose it once filled by the waters of the sea, and that they gradually 

 retired, leaving, as they went, the highest terrace, how is the second terrace 

 to be formed ? Will you let down the land, reintroduce the sea, and bring it 

 again to the foot of Glenartney ? But what would become of the highest 

 terrace, in the meantime, all down the valley, at Kinkell for example? Exposed 

 to tides and waves, must it not have been swept away ? There is yet another 

 difficulty, not less fatal, to which we shall immediately refer. 



Some of our leading geologists, rejecting this view, have held these terraces 

 to be the margins of ancient lakes. The flow of the waters, it is said, had been 

 barred, and our valleys had become the beds of old lakes. From time to 



* Nowhere, perhaps, is this opinion more ingeniously stated and defended than in a series of 

 papers by the late Mr Charles Maclaeen. See his Select Writings recently published, vol. ii. 

 pp. 186-201. It is from the valley of the Tay that he takes his examples. 



