314 



On the Fall of Rivers. 



the sources only of the two rivers are ascertained barometri- 

 cally, and the portion of the Clyde comprising the falls has 

 likewise not been ascertained by levelling instruments ; how- 

 ever, that does not influence the accuracy of the general 

 results, as the exact levels of the Clyde above and below the 

 Falls check the intervening portion. 



The Fall of the Clyde. 



The accuracy of the data both for the Clyde and Tweed, 

 which I ascertained from two lines of levellings quite inde- 

 pendent of each other, are checked by a phenomenon which 

 it might not be uninteresting to record in this place. 



Both rivers are very nearly at the same level near Biggar. 

 This very spot exhibits the remarkable phenomenon of a 



* There are two other falls of smaller dimensions, viz., the Dundaf Linn, 

 > mile below Corra liinn, 4 feet high ; and one which is J mile below Bonnington 

 Fall. The total descent of the river from the first to the last fall — a distance 

 of 3'7 miles, — amounts to 230 feet. 



t The Falls excluded. 



