the North East of Ireland. 20^ 



A mass of chalk, extending about a furlong in the face of the 

 clifTs, is here seen, terminated abruptly, and with every appearance of' 

 violent convulsion at both extremities. Towards the east it is under- 

 lain as well as overlain by basalt, and loses itself, forming a narrow 

 tongue surrounded by that rock. In this quarter a portion of the 

 chalky strata, elsewhere horizontal, exhibits a remarkable curvature. 

 Towards the west the chalk runs far out to sea, forming a sharp 

 and narrow point of land, of which the greatest height is about 70 

 feet. The isthmus which joins this point with the main land, is 



insinuating itself into the fissures, and often converting by its contact chalk into granular 

 marble, while fragments of the chalk, of all sizes, appear to have been forced upwards 

 and imbedded in the basaltic rock, having suifered in their superficial parts where the 

 basalt touches them a most remarkable change. 



It seems impossible to conceive appearances more utterly irreconcilable with the hypo- 

 thesis, that the basalt was deposited regularly above the chalk from a state of aqueous 

 solution. On the other hand, were we to imagine a priori, the phenomena which would 

 probably result from the eruption of a current of ignited lava from beneath the chalk, 

 and its subsequent diffusion over the upper surface of the chalk, while the whole was 

 submerged beneath the sea, and under a considerable pressure, they would exactly accord 

 with those which may actually be observed at Kenbaan. 



To the same purpose the changes effected by the whin dykes of this district on the 

 rocks they traverse might be cited. Thus we have instances : , 



1. Of the conversion of eld red sandstone to hornstone. See page 201. 



2. Of the conrersion of the slate clay of the coal measures to flinty slate, and of the 

 reduction of the coal itself to cinders. See pages 205, 206. 



3. Probably, also, of the conversion of the slate clay of the lias formation into flinty 

 slate. See page 213. 



4. Of the conversion of chalk in several places into granular marble. Seepages 172. 173. 

 Hence, if it be allowable to speculate on subjects so remote from actual observation, I 



would infer that the hypothesis which ascribes the formation of the floetz trap rocks to 

 submarine volcanoes, which were active at a very remote period before the seas and conti- 

 nents had assumed their present relative level, is both in itself more consistent, and in its 

 application to the actual phenomena more satisfactory than any other. 



It is evident that the basaltic mass of Ulster was accumulated antecedently to the last 

 great convulsion which has modified the surface of our globe, excavating its vallies, and 

 constituting its alluvial deposits. 



Vol. III. 2 d 



