CHAP. XI.] HANTONIAN PERIOD. 209 



tricts were the scene of tremendous volcanic eruptions, at 

 first from lofty volcanic cones, and subsequently, in all 

 probability, from huge gaping fissures, which now appear 

 as lava-filled dykes. The lavas ejected from these sources 

 form extensive sheets, which are spread out one over the 

 other, till in some places they still form a pile over 3,000 

 feet in depth. 



At certain localities, in Antrim and in Mull, fl uviatile 

 deposits are intercalated between some of these lava-flows, 

 and consist of gravels, sandstones, and carbonaceous shales ; 

 the shales containing leaves of plants which prove to be of 

 Lower Eocene age, according to Mr. J. S. Gardner. 1 The 

 gravels consist chiefly of rolled flints and fragments of lava, 

 with some pebbles of grey quartzite. In Mull the river- 

 bed containing these deposits can be traced for a distance 

 of nine miles, and the width of its valley seems to have 

 been between a mile and a mile and a half when it was 

 invaded and filled with the lava-flow which now covers it. 

 This stream seems to have come from the north-west, and 

 " a restoration of the contours about the river- gravels 

 shows high ground to the south and east, coinciding with 

 the boundaries of the traps, with the river channel roughly 

 following the present outcrop of the Palaeozoic rocks in 

 the Ross. A spur of gneiss from Benmore, represented 

 by the gneiss of Gribun, Erisgeir, and Inch Kenneth, 

 directed its course westward, and there is but slight trace 

 of it along the shore of Torosay." 2 



Another buried valley lies below the Scuir of Eigg, the 

 dark pitchstone of the Scuir resting upon a thick bed of 

 gravel, which fills a hollow or trench excavated in the 

 underlying basalts, and amongst the gravel are frag- 

 ments and branches of coniferous trees. This interesting 

 relic of an Eocene river was first described by Dr. A. 



1 " Quart. Journ. Geol. Soc.," vol. xliii. p. 270. 



2 Gardner, loc. cit., p. 286. 



P 



