﻿106 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 8, 



wards with the underlying oolitic strata, intervene beds of soft shale 

 and crumbly limestone, 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 Staffm lies at the westernmost extremity 

 of Trotternish. Its northern headland is composed 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 of 

 the shales above the columnar trap, thus brought into contact with 

 the force of the sea ; and as the westernmost extremity of the range 

 of amygdaloidal hills corresponds nearly to the centre of the bay, the 

 ruin of the superincumbent trap is here very great indeed. It was 

 on the shores of this bay that Sir Roderick Murchison and Professor 

 Sedgwick found the blocks of freshwater or estuary limestone referred 

 by them conditionally to the Wealden. 



On landing, I found similar blocks with similar fossils, but could 

 not see them in situ in the section along the coast. I found, how- 

 ever, very soon that the black shales included in and underlying the 

 amygdaloidal trap were fossiliferous, and before long had the pleasure 

 to find numerous specimens of Ammonites cordatus and Belemnites 

 Owenii and Beaumontianus, indicating the age of these shales be- 

 yond a question to be that of the Oxford clay, to which stratum 

 indeed mineralogically they have the most marked resemblance. 



When the tide receded, the beds of shale were exposed in regular 

 sequence along the shore, and beneath them in conformable succession 

 I found in situ the strata of yellowish crumbly limestone and shale 

 with estuary fossils from whence the blocks referred to had been 

 derived. 



The series of beds seen in the section in descending order is as 

 follows : — 



1. Immediately below the amygdaloidal trap, which is crumbly 

 and wackaceous at the junction, there is a thin band of small rolled 

 pebbles mingled with fragments of jet. . 



2. Crumbling blue shales with Belemnites Owenii, Ammonites 

 cordatus, and A. Eugenii, about 5 feet in thickness. 



3. A thin band of concretionary limestone. 



4. Five feet of blue shale with Ammonites and large Belem- 

 nites. 



5. Two bands of hard grey concretionary limestone, weathering 

 yellow, in which I could find no fossils, 3 feet. 



6. Dark blue shales with small Belemnites, 7 feet. 



7. Concretionary reddish and yellowish limestone with large 

 Belemnites, 1 foot. 



8. Blue shales, 1 foot. 



9. Ferruginous sands with fragments of wood, pyritized and in the 

 state of jet, 1 foot. 



10. Concretionary limestone with Belemnites, 1 foot. 



