86 MONOGRAPH OF DURA DEN. 



at Antrim and the Giant's CauseAvay, where alternating leaf- 

 beds and lignites are repeatedly mixed up with amorphous 

 and columnar igneous rocks. The account serves to establish 

 the important geological inferences, that Scotland and Ireland 

 were at the period of the eruptions parts of one and the same 

 country ; that the Hebrides and mainlands were united on 

 both sides ; and that all the marine interspaces were over- 

 flowed by volcanic mud and ashes, which embraced, season 

 after season, the annual sheddings of a forest vegetation. 

 After describing the characters of the lignites and organic 

 remains, and the igneous mass of basalt rock in which they 

 are imbedded, the noble author proceeds to observe : — 



" No one who has followed this description of the Ardtun Head, the 

 ' Point of Waves,' and is acquainted with Staffa, will fail to recognise a re- 

 markably corresponding feature. The lowest two members of the Ardtun 

 series, the massive amorphous basalt, passing into and resting upon the 

 columnar, offer a precise representation, on a smaller scale, of that wonderful 

 front which lies opposite, at some five or six miles' distance. The whole 

 group of the Trishnish Islands, ' which guard famed Staffa round,' would 

 seem, from their low tabular appearance, to belong to the same prolonged 

 slieets of trap, and may represent the skeleton of that country now destroyed, 

 from whose forests the Ardtun leaves were shed. It is not improbable that 

 by future researches amid the conglomerates, and other stratified matters asso- 

 ciated with the traps, in Mull and the neighbouring islands, portions of the 

 more substantial parts of those forests will yet be found. It appears, from 

 Dr. M'Cnlloch's account of the traps of the middle district of the island of 

 Mull, that he did actually find the carbonized stem of a tree, whose structure 

 proved to be coniferous. His notice of the ' vein ' in which it occurred is an 

 accurate description of the tuff which covers the leaves of Ardtun ; but he 

 expressly says, that it occupied a perpendicular instead of a horizontal posi- 

 tion in the cliff ; and the headland of Bourg seems to be indicated, although 

 not very clearly, as the locality." 



Geologists have long been acquainted with the surturbrand 

 beds of Iceland ; that is, bituminized wood embedded in the 

 igneous rocks of that volcanic island. The characters of the 

 two classes of phenomena are almost identical ; a s^'^mpathy 

 betwixt the localities is still maintained by the shocks of earth- 

 quake that, from time to time, reach our shores. Hecla is still 

 in fiery activity, casting up volcanic mud and ashes, and thus 



