OF THE SEA AND LAND. 



better eye than that which determined the vale of the 

 Tay above Birnam to have been once a lake, will dis- 

 cover its antient cataracts in the rock, now a hundred 

 feet above the river, and far removed in lateral position 

 from its present bed. Let those who are so free in the 

 use of deluges, thus learn a lesson of caution in pro- 

 nouncing on what demands a very different eye than 

 that for a stratum or a specimen, and a species of 

 knowledge which geologists have too much forgotten 

 to acquire. Niagara itself is retreating daily ; and 

 when this act of geological suicide shall be completed, 

 some posterity will trace the silent seat of that which 

 was the wonder of our own days. 



The drainage of lakes may be placed at this stage 

 of a river's action ; occurring, as it does, by the low- 

 ering of the original rocky boundary through the cor- 

 rosive powers of the issuing stream ; while I need not 

 dwell on the separate case where the same consequence 

 results from the removal of alluvia, formerly laid down, 

 and producing the barrier. If the lake is obliterated 

 through the accumulation of alluvia, the result will be 

 a plain : in the present case, it must be a valley of 

 some kind, yet not without an alluvial bottom. If the 

 common opinion respecting Thessaly be true, it is a 

 striking case in point, the Peneus being the cause ; and 

 in this manner will the great chain of the American 

 lakes be assuredly drained at some distant day, by the 

 operations of Niagara. If, essentially, Glen Roy was 

 drained in this manner, yet it must have been by sud- 

 den and repeated actions, as is proved by its peculiar 

 phenomena, which I have elsewhere described and 

 analysed. That Loch Maree will, partially at least, 

 undergo the same fate, at some future time, is certain: 

 and if I here remind the reader of the Lake of Con- 

 stance, it is for the purpose of recalling his attention 



