Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/178

 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 specimens 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 interruption, 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; 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