Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/418

408 which separate the different sets of columns, together with the varying inclinations 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 marle. 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 made stratum, not at all flattened. Portions also of trunks of trees retaining their original shape, an seen in the same bed, silicified, and their rifts filled with chalcedony, approaching in aspect to semi-opal.

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 accompanies 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