Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/129

 more numerous varieties which did not come under my observation may be found to exist.

Arriving at the high bridge which crosses the river Awe, the mineralogist will be surprised to meet with a secondary stratum in a situation certainly as unexpected as can well be conceived. A small portion of it only is denuded by the action of the river, and exhibits two distinct beds, the lowermost consisting of the well known red sandstone spotted with white, which occurs near Dumbarton, in Arran, and elsewhere, and the uppermost of a coarse grained white calcareous grit. This stratum is elevated at a small angle, and shelves away towards the side of Cruachan as if it was about to dip under the mountain: its junction with the primary schistus is not visible. I could not trace it upwards on the opposite side of the river in the direction of the stratum, although it is probable that from the red colour of the soil some portion of it exists where the road is made. It may be traced a little way down the course of the river, but the ground being much encumbered and difficult to examine, it soon disappears. I attempted in vain to find it on the flat tract at Bunawe, nor did I succeed any where from Tyanuilt to the sea in recovering any portion of this stratum; the low land being always covered with alluvial matter, and the denuded rocks appearing every where to consist of schist and granite traversed by veins of porphyry. It affords a remarkable example of a deposit of secondary rock, not many hundred yards square, entangled in the middle of a primary district, and separated, apparently by many miles, from any other similar rock. I shall hereafter however attempt to give a general sketch of the connection of Cruachan with the surrounding country, when the recurrence of the same circumstance will be described, which, if it diminishes the surprise at first excited by its solitary and unconnected appearance here, increases its general interest,