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XXV.—Notice of High-Water Marks on the Banks of the River Tweed and 
some of its Tributaries; and also of Drift Deposits in the Valley of the 
Tweed. By Davtp Mitne Home of Wedderburn, LL.D. (Plates 
XXXV.-XXXVIIL) 
(Read June 7, 1875.) 
A few years ago, a memoir on high-water marks on the banks of the Rivers 
Earn and Teith, in Perthshire, by the Rev. THomas Brown, was read in our 
Society, and published in our Transactions. 
The only other Scotch geologist, so far as I know, who has alluded to the 
existence of river terraces, much above the level of existing floods, is the 
late Dr Ropert CuampBers. In his work, entitled “ Ancient Sea Margins,” Dr 
CHAMBERS specifies many Scotch rivers, in the valleys occupied by which, he 
had seen terraces, at considerable heights above the rivers and above the sea. 
The explanations of these high river terraces given by the Rev. Mr Brown 
and by Dr CuamBers respectively, are different. I venture to entertain doubts 
respecting the soundness of both explanations ; and as the subject is of some 
interest, it appears to me that farther inquiry is desirable. 
Dr CHAMBERS was under the belief that almost all the high-level terraces 
examined by him on the Tweed, Tay, Clyde, and Spey, were horizontal, and 
therefore not formed by rivers. He did not suggest, that they had been formed 
by lakes. He considered them sea beaches. 
The Rev. Mr Brown, on the other hand, states that all the high-level 
terraces which he examined on the Rivers Earn, Teith, and their tributaries 
the Turrit, Keltie, and Ruchil, slope with the streams; and he ascribes their 
formation to river action. He however came to this rather remarkable 
conclusion, that the highest of these terraces on the Earn, which is about 57 
feet above the channel of the river, and in like manner the highest terraces 
in the other four rivers, had been formed by floods in these rivers, whilst flowing 
im their present channels ; to account for which floods, he supposes the existence 
of what is called “a pluvial period” in Western Europe. The floods in the 
Earn now, seldom rise higher than 10 or 12 feet. A rise of the river in its 
existing valley, of 57 feet, certainly would imply a climate and state of things 
very different from the present. 
Startling as this conclusion appeared, I found that it had been also suggested 
by another geologist, Mr ALFrep Tytor, in explanation of the high terraces of 
VOL. XXVII. PART IV. 6 U 
