460 MR MILNE ON THE DRYING UP OF THE 



not to warrant the explanation which Professor Phillips has suggested. I find 

 that these remarkable occurrences happened, the one in October, and the other in 

 April ; so that they occurred at a time of the year, when the frost may have pro- 

 duced them. 



But though frost appears to have had, at all events, a principal share in ac- 

 complishing the desiccation of the rivers on the 27th November last, it is at first 

 sight not easy to see precisely the manner in which it operated. The frost then 

 was not nearly so intense, or so long continued, as at other times, when, how- 

 ever, similar results did not occur. On the 27th November, the thermometer, in 

 the south of Scotland, did not sink below 25° Fahr. But, in the previous winter, 

 it will be remembered, that, in the south of Scotland, it sunk as low as 5°, and 

 that, for a period of about ten days continuously, it was below 27°. Yet none of 

 the larger rivers stopped during the continuance of this frost, and it was only ob- 

 served that they were somewhat lower than usual. It is not easy, at first sight, 

 to perceive how the frost acted, so as to produce on this one occasion, phenomena 

 which it failed to produce on other occasions, when it was both more intense and 

 more protracted. 



1. It has been suggested, that the ice formed on the lip or edge of the dam- 

 heads, arrested the current, and thus dried up the channel in inferior parts of the 

 river. At Ormiston MiU, on the Teviot, a dyke or barrier of ice, from sixteen to 

 eighteen inches high, traversed the entire width of the river, and for several hours 

 prevented the current from flowing towards Kelso. It was observed also, that the 

 formation of this icy barrier was greatly assisted by a strong easterly wind, which, 

 by raising a spray on the lip of the damhead, allowed the water along the line of 

 the cauld to be rapidly reduced to the temperature of the wind. 



The effect here described would no doubt be produced, and the explanation 

 may be sufficient to account for the drying up of the Teviot in one part of its 

 com-se ; and perhaps it might answer also for some of the other rivers which run 

 towards the east, and that are crossed by damheads above the places where the 

 stoppage occurred. But the explanation is much too partial and too local to be 

 the true one. 



(].) For, according to it, the same phenomenon should occur almost every 

 winter, as there is often a frost accompanied by a high wind, which, whatever be 

 its direction, would blow against the stream of one or more rivers in some part 

 of the country. Now this phenomenon, so far from happening every winter, is 

 of very unfrequent occurrence. 



(2.) But, in the next place, the explanation fails entirely in regard to those 

 parts of the rivers where there are no damheads ; and it has been seen, that, in 

 the Slitrig, the Euchan, and a number of other rivers, the waters disappeared in 

 those parts of their course which are situated above any damhead. 



