168 Dr. Mac Cul loch's Supplement to the 



which the ordinary limestone appears to pass into the marble, can 

 also be traced, although in consequence of the irregular nature of 

 the ground they are widely dispersed. I ought also to add that in 

 one of these intermediate portions I found layers and scattered spe- 

 cimens of bodies having the general aspect of those obscurely 

 organized fossils which have been all confounded under the name 

 of alcyonia, consisting of a calcareous carbonate whiter than the 

 surrounding rock, their surfaces being covered with minute but 

 irregular crystals of the same substance, and being so much more 

 durable than the surrounding materials as to remain protruding 

 after these have been washed away. 



To the topographic detail as given in the original paper, I must 

 now also make an addition, the nature of which will be better 

 understood by inspecting the improved map. 



The strata on the Broadford shore may be traced to a place 

 opposite Scalpa, but without a name, where they terminate in a 

 succession of beds consisting of the shale only. After some inter- 

 ruption, in consequence of the intrusion of a mass of syenite and 

 trap, a small patch of irregular limestone is seen, which soon ceases 

 in consequence of the renewal of the syenite, not to appear again 

 till we arrive at Loch Sligachan. 



On this shore the overlying position of the syenite can be easily 

 traced at the places of contact, demonstrating that it here combines 

 the same double relation to the stratified secondary rocks which it 

 is found to bear elsewhere j cutting through them at the same time 

 that it covers them. 



The boundary between the upper portions, or the north-western 

 line of the Strath limestone and the syenite, is extremely irregular, 

 although it is not often possible to procure a sight of the actual 

 contact, or even of the probable junction of these different rocks. 

 It is however a sufficient proof of that irregularity, that as marble 



