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EEV. THOMAS BEOWN ON THE OLD EIVEE TEEEACES 



terrace system of the Ruchil is feebly represented by the 12 or 14 feet 

 banks which are continued along the Earn, past Dunira, and on to the loch. 

 In seeking the explanation of this difference a remarkable circumstance was 

 brought out. The floods which come down the Earn at the present day are 

 quite feeble compared with those of its tributaries. The Ruchil is remarkable 

 for the suddenness and strength of its floods, while the flow of the Earn is 

 quiet and equable. Now, the height of the old terraces on the two streams 

 exactly corresponds with this. The coincidence is striking, and can have only 

 one meaning. Along the stream, where the floods are still powerful, the 

 old terraces are powerfully developed. Along the stream, where the floods are 

 feeble, the old terraces are feebly developed. The only possible conclusion is, 



Sketch 15. — On the Upper Earn. 



that it was by the floods of these rivers that the old terraces were really built 

 up in a former age, and that their flooding power was then in proportion to 

 what it is at present. 



A second circumstance of the same kind is seen when we compare Loch Earn 

 with Loch Lubnaig. Along the shores of the latter, as we have already shown, 

 there are well marked terraces, and on Loch Earn also a similar deposit is 

 present, but in far less proportions, spreading out especially towards the bottom 

 of the lake, where in September 1869 I found it 12 to 14 feet above the water. 

 This is a weak representative of the 37 feet terrace of Loch Lubnaig. But 

 the remarkable thing is that it almost exactly corresponds to the proportionate 

 rise and fall of the water in the two lochs at present, as caused by a flood on 

 the one hand, and a drought on the other. Both lakes, I was told, were at the 

 lowest ebb at which they had been seen for years. In the case of Loch Earn, 



