256 0N TIIE BASALTIC COUNTRY IN IRELAND* 



Additional evi- nature had made any change in her materials or their ar- 

 Stic n hum- rangement, hoping that at the junctions of the^e little sys- 

 mocks. terns we should find some facts, that would throw Tigbt on 



the subject; but we generally failed; want of perpendicu- 

 larity, or other local circumstances, impeding us at the most 

 interesting points. 



On the present occasion she has adopted an opposite line 

 of conduct, and in many of the steps she has taken, ob- 

 trudes upon us demonstration of what she has done. 



Whoever has attended to the exertions of man, when em- 

 ployed in altering our present surface, either by levelling 

 heights, or by making excavations, must have observed that 

 it is the practice of the workmen to leave small, cylindrical 

 portions standing, for the purposes of determining the 

 height of the old surface, and thereby ascertaining the 

 quantity of materials removed. 



To these may be compared the stratified basaltic hum- 

 mocks so profusely scattered over our area, and which seem 

 to show how high our quondam surface once reached. 



The hummock of Dunmull, three miles south-east from 

 Portrushy is very beautiful; it stands on the top of a high 

 ridge, and is a conspicuous object from all parts of the 

 country; it is exactly circular, its flat surface contains an 

 acre, it is completely surrounded by a perpendicular facade 

 about twenty-five feet high, and formed by two strata, a 

 columnar, and an irregular prismatic resting upon it. 



From this elevated station, where I had the pleasure of 

 accompanying you, I showed you at six or seven miles dis- 

 tance to the westward, among the Derry mountains, the still 

 loftier hummocks of Altabrian and Sconce, hemispherical 

 in form, composed of but one stratum each, while their 

 swelling-out bases displayed accumulations of many more: 

 and also near the hummock of Fermaylc, resembling Dun- 

 mull, but much larger, and also surrounded by a facade 

 composed of two strata. 



i showed you also at twenty miles distance to the south- 

 east the gigantic Slcmish, one of our basaltic hummocks, 

 magnified (as it were) into a lofty and insulated mountain, 

 completely stratified from its base to its flat summit. 



I showed you likewise from the bottom of its ridge the 



neat 



