Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/515

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505
Dr. Mac Culloch on Staffa

To those who have seen the beautifully regular columns of the Giant's Causeway, those of Staffa will appear rude and comparatively shapeless. They no where exhibit that accuracy of design which is so conspicuous in the former, and are rarely seen of any considerable length without some incurvation. But their thickness is much greater, since they often attain a diameter of four feet. They vary perpetually in the number of their angles, the pentagonal and hexagonal being the most common, and those of an inferior number of angles being less common than those of a superior. Their joints are very irregularly placed, and are frequently wanting through a considerable length. When separated, the touching surfaces are either flat, or marked by a slight respective concavity and convexity. In many places, and most conspicuously in the great cave, the angles of the upper joint are considerably and obliquely truncated at the point of contact with the lower one. But I did not perceive any instance where a corresponding projection of the end of the inferior angle rose to cover the truncation, a circumstance of such frequent occurrence at the Giant's Causeway. I may add, that the articulated columns are most remarkable in the great cave, and that the straightest columns generally exhibit the most frequent articulations. The curved columns visible at the cave called the Clamshell cave, extend for 40 or 50 feet without a joint.

The disposition of the variously curved columns above this small cave, is perhaps one of the most striking features of the whole island. But it will be time enough to speculate on the formation of a curved basaltic column, when we have something rational to offer on that of a straight one.

A very extraordinary aggregation of columns lies off this cave, forming a conical detached rock, corruptly called Boo sha la. The Gaelic name Buachaille (Βουχόλοç?) the herdsman, is commonly ap-

Vol. II.3 s