402 The Parallel Roads of Glen Hoy. 



Mr Darwin's memoir connects together, and furnishes a 

 key to a vast number of phenomena. In looking back to our 

 own notes, taken on a visit to Glen Tilt, in 1828, we find va- 

 rious facts which the principle he has evolved may serve to 

 explain. We find, for instance, terraces of gravel marked as 

 existing at the following localities : 1. In the open country 

 between Perth and Dunkeld, forty or fifty feet above the 

 waters of the Tay ; 2. At Logierait, a large table-shaped ter- 

 race, sixty or seventy feet above the flat land bordering the 

 river, and probably 300 feet above the sea ; 3. At Auld Clu- 

 nie, above Killiecrankie, terraces at various heights — from 

 150 to 400 feet above the river, and probably from 400 to 700 

 above the sea ; 4. In Glen Tilt, near Glen Criny, remnants of 

 terraces ascending to the height of 100 to 150 feet above the 

 stream, and 750 or 800 above the sea. On the top of these 

 last, and on the south side of the stream, we found boulders 

 of granite of one or two tons weight, belonging either to the 

 rock on the opposite side of the deep ravine, or to some more 

 distant locality. These alluvial terraces have generally deep 

 cuts or gullies in them, displaying their structure and mate- 

 rials. Even the lowest ones, such as those between Perth and 

 Dunkeld, can only be well accounted for by assuming, that 

 the Tay formerly fell into a sea which stood forty or fifty feet 

 higher than that which now receives its waters. 



The perfect horizontality of the terraces of Glen Tilt and 

 Glen Spean, prove that the levels were not sensibly disturb- 

 ed over a space of twenty miles square, by the upheaving 

 movement. Judging from the case of Sweden, we may even 

 suppose that the rise was simultaneous, and nearly equable 

 over all Scotland. We may hence infer, that when the up- 

 per terrace of Glen Roy was formed, Scotland consisted of 

 an archipelago of islands, with one broad firth in the middle, 

 and numerous narrow straits, canals, and inlets traversing its 

 southern and northern divisions.* 



* Notwithstanding tlie strong case Mr Darwin and his geological friend 

 have made in support of their speculation, we are not disposed to go along 

 with them, but rather to consider the Glen Eoy and other similar terraces, 

 as formed by the emptying of salt or fresh water lakes. The objections to 

 the lake hypothesis, offered by some geologists, are not valid, owing to 

 the subject being viewed by them on the small scale. — Edit. 



