Professor E. Forbes on the Oolite in Skye. 95 



Diagram of the Geological Structure of Trotternish in Skye, 



a. Lias, «• Estuary shales. 



b. Inferior oolite. /• Oxford clay. 



c. Middle oolite. g. Amygdaloidal trap. 



d. Imperfectly columnar basalt. 



The strata of the cliffs dip rapidly inland southwards at a 

 considerable angle, and a little way behind them towards 

 the east. Farther back towards the west rise lofty hills of 

 amygdaloidal and zeolitic trap, which broken up into frag- 

 ments on these escarpments, form magnificent isolated 

 blocks and pinnacles of rock of vast height and slenderness, 

 resembling so many gigantic castles and towering spires of 

 dimensions beyond the workmanship of human architecture. 

 The truly wonderful scenery of the Storr and Quiraing, which 

 far surpasses for irregularity any other rock landscapes in 

 Britain, have been produced by the breaking up of this 

 amygdaloidal escarpment. 



The cause of this extraordinary range, extending over 

 many miles of cyclopean ruins, depends upon the fact which 

 it is my object to announce in this communication. Between 

 the mass of amygdaloidal trap and the columnar trap which 

 crest the sea-cliffs and dip inwards with the underlying 

 oolitic strata, intervene beds of soft shale and crumbly lime- 

 stone, the wearing away of which causes the breaking up of 

 the superincumbent mass, the retrocession of the main body 

 of trap, and the isolation of the blocks and pinnacles, which 

 probably become more numerous after every winter. 



The open bay called Loch Staffin lies at the westernmost 

 extremity of Trotternish. Its northern headland is com- 

 posed of the oolitic beds and superincumbent columnar trap 

 dipping southwards, and its southern by the same traps 

 rising again to commence a new line of coast, forming the 

 southern bound of the peninsula. The bay itself has been 

 formed in consequence of the wearing away by the waves 



