RIVERS TEVIOT, NITH, AND CLYDE. 4g| 



(3.) But even where there are damheads, this explanation is unsatisfactory ; 

 for, if the current was there obstructed, the water should have accumulated above 

 them, and, so far from a want of water being experienced by the millers in their 

 mill-leads, there should have been an unusual supply. But all the mills, except 

 one, on the different rivers and their tributaries, were stopped from want of 

 water. 



(4.) In the fourth place, if the waters were thus merely arrested for a time, 

 and not abstracted or excluded from the channels, there would be a prodigious 

 overflow, or, in other words, a tremendous flood, after the obstruction was re- 

 moved ; and, moreover, the water would not begin to flow again gradually, but 

 would burst forth with sudden and irresistible impetuosity. These effects, how- 

 ever, are inconsistent with what was observed on nearly all the rivers where the 

 phenomenon occurred. The Clyde only is said to have been a little flooded and 

 muddy on the 28th November, — which can be accounted for by the sudden thaw 

 which, by that time, had taken place. The flow had recommenced, however, the 

 •preceding evening, and it came on gradually. 



2. Another theory to explain the phenomenon, might be founded on the re- 

 markable fact, that, during the night of the 2t)th, and morning of the 27th No- 

 vember, there was ice formed in large quantities at the bottom of the rivers, which 

 must, to a certain extent, have obstructed the flow of the water. 



(1.) But it appears to me, that this would have had a very opposite effect 

 from what occurred ; for, if the velocity of the current is generally diminished 

 throughout the whole course of the river, must it not happen that the waters will 

 be less rapidly drained off, and thus, so far from the waters entirely disappearing 

 from the bed of the river, or even diminishing in it, they would appear considerably 

 swollen. 



(2.) This effect would be rendered all the more striking, as, by the supposi- 

 tion, the bottom of the river is raised by the formation of ice on it. So long as 

 the river continues to draw its wonted supplies from the springs which feed it, 

 the circumstance of ice forming on its bottom, so far from tending to lower the 

 level of the current, would tend only to elevate it. 



(3.) Besides, if this were the true explanation, the phenomenon ought to 

 happen every ivinter, and indeed almost every frost which occurs ; because I believe 

 there are few frosts, during which ice does not form at the bottom, with even 

 more readiness than on the surface, of running streams. 



I may here mention, that the formation of ice at the bottom of running 

 streams, has been frequently observed in the continental rivers, and especially 

 the Elbe. But it was never known that the}'^ stopped running, or even diminished 

 in volume, at this period. On the contrary, they were then observed to be ge- 

 nerally swollen. 



VOL. XIV. PART II. 4 c 



