1873.] • BRYCE JURASSIC ROCKS OF SKYE AND RAASAY. 329 



within the tideway. The thickness at the highest part of the low 

 cliff it forms was found to be 36 feet to half-tide level, total thickness 

 unknown, as it descends below low water. On this doleritic sheet 

 as a base, and between it and the common overlying trap, the Loch- 

 Sfcaffin beds are placed. It occupies the tideway to the point where 

 the cliffs lower by the thinning of the upper beds and the denuda- 

 tion of the trap. The following Section was obtained under the 

 high basaltic precipices about one mile east of the S.E. angle of the 

 bay, and a little to the west of a fault which throws the beds 30 ft. 

 down "towards the east. 



Section VII. 



Loch Staffin (order descending). 



1. Basaltic covering, 60 to 70 ft. 



2. Limestone and dark shale, 3 to 4 ft. 



The upper bed next the basaltic rock is altered to the depth of 12 or 15 

 inches ; the lower part of this is banded and cherty, like a blue-black 

 Lydian stone, with crystalline shining surface, in parts ; the upper part, 

 that in contact, is not banded, and closely resembles the fine-grained 

 lowest layer of the basaltic rock itself. 



3. Sandstone bed, yellow, weathering white, 4 to 5 ft. ; Neritina staffinensis 



and a short oval Unio occur. 



4. Dark altered clays and shales, with shelly courses, 4 or 5 ft. ; the fossils are 



Potamomya Sowerbii, Cyrena Jamesoni, Pholadomya acuticostata, Perna 

 Murchisoni, Corbula MacNeillii. 



5. Limestone band, 4 ft. 



6. The Ostrea-hebridica bed, about 7 ft. This bed consists throughout, 



wherever it is seen, of a mass of oyster-shells cemented together by a 

 muddy paste so closely that it is very difficult to obtain a perfect shell 

 for determination of characters. The bed has great horizontal extent 

 along these cliffs ; and interrupted patches occur in several places east- 

 wards connecting with the Portree cliffs ; throughout it has the same 

 structure. How inconceivably prolific must have been the oyster-beds of 

 the period ! 



7. Sandrock, white and yellowish-white, about 25 ft. ; with layers of carbona- 



ceous matter parallel to the stratification, and pieces of jet. It contains 

 angular bits of quartz, Gyrenes, chiefly in the upper part, and Neritina 

 staffinensis. It is traversed horizontally by huge dark-coloured bombs, 

 effervescing briskly with acid, and leaving a sandy deposit where they 

 decompose out. 



8. Arenaceous limestones, G or 7 ft. 



9. Thin-bedded flaggy limestones, 2 or 3 ft. 



10. Black crumbling soft shales, 2 to 3 ft. 



11. Grey calcareous and sandy shales, with Cyrence and oysters, probably 10 or 



12 ft. Total of Oolitic beds about 70 ft. 



12. The dolerite sheet extending under low water. The lowest Oolitic beds in 



contact with it are altered to the state of a saccharine marble ; they 

 adhere firmly to it ; it insinuates itself among the beds in all directions, 

 and entangles isolated portions of them in its mass. The evidence is 

 thus even more complete than in the cases already given for the intru- 

 sive character of this rock, and its posteriority to the Oolitic series. 

 Those portions of the limestones which are most altered still retain 

 their carbonic acid, showing that the change took place under great 

 pressure. The lowest series of beds probably exists underneath it. 



It is difficult to bring any two sections of these beds into exact 

 harmony : with certain beds of a normal character others of a varying 



