206 On the basaltic 1 Surface of the Counties 



Knock Lnughran, near Maghera, and a tall hummock (whose 

 name I forget) a mile eastward from LisanoUre* 



We meet still more frequently an imperfect style of hum- 

 mock, a semicircular facade one side, while on the other 

 it slopes away gradually with the dip of the strata, as if the 

 operation had been interrupted before it was carried quite 

 round ; the most remarkable of these are Bally strone, in 

 Deny, and Croaghmore, in Antrim, both visible from 

 Dunmull. 



Regular stratifications on the summits of hills and moun- 

 tains have been long a stumbling-block to theorists ; the 

 historian of the French Academy, for the year 1716, ob- 

 viously ascribing the superficial inequalities of the earth, 

 (like many others) to causes acting from below, and per- 

 ceiving how incompatible such assemblages of strata were 

 to his theory, thinks it safer to doubt their existence, as they 

 could not have been formed, he says, " unless the masses of 

 the mountains were elevated in the direction of an axis per- 

 pendicular to the horizon : ce que n" a pu etre que ires rare" 



But as these stratified mounts are in our area by no means 

 uncommon, they lay us under the necessity of suggesting 

 another alternative similar to those we have already stated. 



Were these isolated hummocks originally formed as they 

 now stand, (solitary and separate from each other) one by 

 one; or, are they the last remaining portions of a vast con- 

 solidated mass, of which the intermediate and connecting 

 strata have been carried off by causes with which we are un- 

 acquainted ? 



To be able satisfactorily to resolve this alternative, it be- 

 comes necessary to take a careful view of the contiguous 

 countries, and to try whether their construction, and the 

 arrangement of their strata, will throw any light upon the 

 subject. 



When we examine the assemblage of hummocks above 

 Knockmult, that is, Sconce, Fermoyle, and Altabrian, we 

 find their materials and stratification precisely similar to that 

 of the country below them to the eastward, where the abrup- 

 tions of the strata are displayed in long stony ridges—- to the 



south,, 



