XI. An Account of Observations, made by Lord Webb Sey- 

 mour and Professor Play fair, upon some Geological Ap- 

 pearances in Glen Tilt, and the adjacent Country. Drawn 

 up by Lord Webb Seymour. 



(Read May 16. 1814.^) 



1. r I 1 HE river Tilt is a principal branch of the Tay, which 

 JL rises on the borders of Aberdeenshire, and runs to- 

 wards the south-west, through the north-eastern part of the 

 county of Perth. A portion of the valley along its course, for 

 about ten miles above Blair of Atholl, is called Glen Tilt. 



2. The adjacent country presents the common character of 

 the Highlands. It is mountainous and rugged, and the surface, 

 except in the lower parts of the valleys, is chiefly covered with 

 heath. Peat-moss frequently occurs. The rock beneath con- 

 sists entirely of those substances, which belong either to the 

 Primitive Formation, or the Overlying Primitive Formation, of 

 Werner, and of which the stratified part is by Dr Hutton 

 denominated Primary. This account is warranted by all the 

 observations which have been made upon these mountains j 

 and their general aspect furnishes a confident inference for the 

 whole. To the north and north-east, the mountains about the 

 head of the river Dee, two or three of which are little inferior 



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