253 



With reference to tlie cause of tlie phenomenon, it was stated, 

 that various explanations had been suggested. Some persons had 

 attributed it to tiie high wind obstructing the flowing of the current ; 

 others, to \\ie frost in forming barriers of ice on the caulds or dam- 

 heads ; others, again, had suggested that the phenomenon might be 

 connected witli an earthquake. In support of this last theory, it 

 was mentioned, that Professor Phillips had, in a recent work on 

 geology, attributed to this cause the drying-up of the English rivers 

 Trent and Medway in the 12th century. 



Mr Milne stated that he adopted none of these views, and that 

 he thought the phenomenon might be accounted for by the united 

 action of the frost and wind which prevailed during the night of 

 the 26th November. After four o'clock that afternoon, the ther- 

 mometer all over the south of Scotland sunk to 26^, at which point 

 it remained for several hours. Accompanying this frost, there 

 was a gale of wind from the east, which had the efl^ect of very 

 rapidly reducing the temperature of exposed and unsheltered spots. 

 In this way, the small and shallow streams flowing in open drains 

 and rivulets, or oozing through mosses and marshes in the hills, 

 were soon frozen and arrested. But, on the other hand, larger 

 bodies of water flowing rapidly in the main channels, at a lower 

 level, and sheltered by high or wooded banks, could not in the same 

 space of time lose enough of their temperature to be frozen. The 

 waters thus ran ofl^, without the usual renewal of supplies from the 

 sources, so that the charmel or bed of the river became speedily 

 drained. 



The reason of this phenomenon not happening more frequently 

 appears to be, that there is very seldom a gale of wind in this coun- 

 try accompanied by a severe frost ; .ind even on this occasion, the 

 frost was not equally intense over the whole island. When a se- 

 vere frost sets in, there is usually but little wind, so that the water 

 in the ujiper parts of the river, is not liable to be cooled more ra- 

 pidly than in the lower and more sheltered parts of its course. 

 Though the sources will, in that case, t6 a certain degree, be frozen, 

 and so, part of the usual supply cut off, the main body of the stream 

 is frozen likewise, whereby the velocity of its current is diminish- 

 ed, by the obstrnrtion of the ice at the bottom and at the surface 

 of the current. So that if only half the usual supply is furnished 

 to the river from its parti.illy frozen sources, there will be no di- 

 mimition in the quantity oi water flowing in the main bed of the 



