276 



Proceedings of the Royal Physical Society. 



-""^JSlorlhBTiclge 



flood of less than an hour's duration upon the Dollar Burn irf 



1877.* A portion of this map, 

 illustrating the unfailing tendency 

 of a flowing stream to throw itself 

 from side to side as it goes, and 

 its method of carrying its bends 

 along with it, is here transferred 

 (Fig. 6). 



This stream was described by 

 another writer as — " Sweeping out 

 to right and left in great curves, 

 eating away the ground, which was 

 largely composed of big boulders, 

 in a fearfully rapid manner," so that 

 the onlookers had to pace back- 

 wards " with regulated steps." "|- 



The travelling of the curves in 

 a river gives to it some degree of 

 resemblance to a line laid out upon 

 the floor and shaken into lateral 

 undulations by a movement of the 

 hand. But in the river this move- 

 ment is necessarily very irregular. 

 In order that curves should travel 

 in a regulated succession it would 

 be necessary to arrange a balance 

 between the force and the resist- 

 ance which it is obviously im- 

 possible to maintain. The banks 

 are attacked at constantly varying 

 angles ; the materials encountered 

 PartofaStreamatDollarasaf- ^''^ seldom for any distance uni- 

 lected by Flood. Thick black lines form. Nor do these considera- 



indicatechanf?esiuthebanks(after ^. , , ^ ^i ^^nn 



And. Taylor, Proc. Roy. Phys. tions apply less to the different 

 Soc, Edinb., vol. iv., p. 220). p^^ts of the same curve than to 

 different ones. Our northern valleys, of date older than the 

 glacial period, usually present, first, an inner flooring of 



* Proc. Roy. Phys. Soc, Edinb., vol. iv., \^. 220. 

 t Trans. Geol. Soc, Edinb., vol. iii., p. 170. 



Fig. 6. 



