small, unless the contraction be very great in proportion. to the diameter of the pipe.
Rocks, on the Surface of the basaltic Country in the Counties of Derry and Antrim. Addressed to Humphry Davy, Esq. Sec. R.S. By William Richardson, D.D. Read March 17, 1808. (Phil.
Trans. 1808, p. 187.]The general design of this paper is to show the great distance to which the same strata may be found to extend, or to have extended, over the surface of a country, and thereby to explaiu the existence of small detached portions of the same species of matter at considerable distances from each other, as having been originally connected by continuity of the same material over the whole surface of the coun- try, whatever be the present interval, and whatever he the quan- tity of matter which such an hypothesis supposes to have been re- moved.
The basaltic area which comprehends most part of the county of Antrim and a portion of Derry. appears to Dr. Richardson peculiarly favourable to such speculations, uncommonly regular in its stratifi- cation, and highly favoured by nature in the frequent exposure of the strata in their abrupt and precipitous terminations.
In the island of Ratblin, more especially, the original features are most happily displayed, and are still in good preservation.
It is in the periphery at the northern side that the sections are seen to the greatest advantage, as the perpendicular facades are often continued for miles together.
Of these facades, four are more distinguished for their grandeur and beauty than the rest,—Magilligan, Cave Hill, Fairhead, and Ben- gore. The two former are the extreme points of the N.W. and SE. diagonal, and are forty miles asunder; at the summits of mountains, accessible by land. The twu latter are visible only from the sea, but are more diversified and more curious in their structure.
The promontory of Bengore, which is nearest to the place of Dr. Richardson’s residence, has principally engaged his attention; and the minute description of its strata forms a considerable portion of his memoir, for the purpose of showing the station which the Giant’s Causeway occupies in the arrangement of the promontory, and also for the purpose of noticing several facts, which he thinks likely to throw light upon the operations performed on our globe since the period of its consolidation.
In the order of the description, Dr. Richardson first gives a gene- ral sketch of the promontory when approached from the west, with an account of the inclination, ascent, culmination, and dip of its strata. Of these he enumerates as many as sixteen, and observes that these are all cut perpendicularly in eleven different places by those mighty walls called in Scotland whyn dykes.
These all reach from the top of the precipice to the water, out of
