ORIGIN OF BASALT. ' 281 



From Dimluce to Seaport, the facade (here the base of the Facts and ob- 

 arrangement) is composed of strata of tabular basalt; upon servations re- 



1 • . , , , ■ t -r-. n specting basalt 



which are accumulated, up to the summit ot Dunmull, co- in the county 



lumna strata, mixed With others, of the variety called irregular °} Antrim; ad- 



^ duced to show 



prismatic. that it is not 



East from Carrickarede, the base of the facade is white volcanic. 

 lime-stone ; upon which, as long as it continues perpendicular, 

 we find ochreous and columnar strata alternaling ; while the 

 hill of Knocksoghy, above, is an uniform alternation of colum- 

 nar and irregular prismatic. 



The strata, forming the promontory of Bengore, are more 

 irregularly mixed: six of tabular basalt, five columnar of four 

 different varieties, three ochreous, and two irregular prismatic, 

 sixteen in all: of which, after the tabular that forms the base, 

 no two of the same kind are contiguous to each other- 



The volcanist will see that he must find a distinct volcano 

 for every separate little system surrounding our area; and 

 that he must make the same crater emit different varieties of 

 lava, and frequently by alternation. 



Fourthly. An examination of -our ba?:alt strata, taken sepa- 

 rately, and so compared with distinct currents of lava, will, I 

 apprehend, turn out a-^ little favourable to their volcanic origin 

 as the comparison of their masses appear to do. 



Whoever has read Mr. Desrrrarest's.Memoir, or even my quo- 

 tations from it, must admit that, if his theory be well founded, 

 all our basalt strata must have once been currents ol liquid 

 lava, and, of course, should resemble those known to have 

 issued from existing volcanos. But, I apprehend, instead 

 of similarity, the most decided differences, will be found be- 

 tween them. 



Currents of lava, we ^re told, are always narrower and 

 deeper, in the vicinity of the crater, broader and shallower, as 

 'farther removed from it: but our basalt strata are of uniform 

 thickness in their whole extent. 



There is another point of view in which the difference be- 

 tween basalt strata and currents of lava is still more decided. 

 Sir William Hamilton, Ferber, Spalai\zani, and even Mr. Des- 

 marest himself, inf/rms us, that, in all currents of lava, the 

 materials composing them are invariably arranged, in a regular 

 gradation, according to their specific gravities : thus, at the 



lowest 



