408 Dr. Mac Culloch on the Geology of 



which separate the different sets of columns, together with the 

 varying incUnations of these beds, seem to mark different sets of 

 deposits. The whole promontory lies on a bed of compact grey 

 limestone, generally indeed approaching to the character of a stone 

 marie. This bed is three or four feet thick, and rests on a still 

 lower bed of hard reddish sandstone, beneath which nothing is 

 visible. Large masses of wood, bituminized and penetrated with 

 carbonat of lime, are found in the marie stratum, not at all flattened. 

 Portions also of trunks of trees retaining their original shape, are 

 seen in the same bed, silicified, and their rifts filled with chalcedony, 

 approaching in aspect to semi-opal. 



Assynt, 



I have separated the account of the limestone which accompanies 

 the quartz rock of Assynt hereafter to be described, and which 

 forms so conspicuous a range of hills, because its connection with 

 that rock is tolerably obvious, and throws no light on its history. 

 But its peculiarity of character, and the great space which it occupies, 

 render it highly deserving of notice, as I believe Scotland no where 

 affords a tract of limestone so extensive. 



A low chain of hills commences about Achamore, and accom- 

 panies the Tain road towards the east for four or five miles, lying 

 as it were in a large valley bounded on both sides by an interrupted 

 range of quartz mountains. It appears to rise gradually as it extends 

 eastward, and about the Kirk of Assynt attains a height of 1200 or 

 1400 feet, forming a large and magnificent continuous mountain 

 ridge, exhibiting a great mural face of precipitous rock to the south, 

 and shelving away to the northward. The dip and direction of 

 the quartz mountains appear in this place to be similar to those of 



