Mr Hugh Miller on River- Terracing. 285 



loops of the Tweed below Old Melrose, shown in Sheet 25 

 of the " Geological Survey of Scotland," and here transferred 



(Fig. 11). 



Each of the loops resembles a quarry, whicli the quarry- 

 men are engaged in extending into the hill-side, deepening 

 it — so far as they can without accumulating drainage — as 

 they go. But some of the workmen now and then turn 

 back from the quarry-face and work at the sloping floor, 

 and convert it from an inclined plane into a series of 

 steps. 



This illustration will perhaps help to make it more evident : 



River Loops on the Tweed below Melrose, showing their effects in the 

 production of Terraces (1, 2, 3, 4. etc.). (From Sh, 25, Geological Survey- 

 Map.) 



Scale — 1 inch to a mile. 



(1.) that the superficial extent of the terraces bears some 

 rough proportion to the size of the loop; (2.) that the 

 accreting bank with its incipient terraces is commonly lower 

 than the side answering to the quarry-face ; * and (3.) that 

 the terraces, if truly belonging to this variety (a fact which 

 is often difficult to establish), are formed independently 

 within each stream-loop, and in no two need be of the same 

 height. Coincidences do necessarily occur; impulses there 



* The nicety with which this rule is sometimes carried out is illustrated 

 by the measurements given in Fig. 16, although the terraces there shown 

 can hardly be called amphitheatre terraces. 



