arrangement even one step further, since I have shown that perfectly characterized clay slate is here a member (to use the Wernerian language) of the flœtz rocks; the sandstone here described being analogous to the old red sandstone of that school, and a member of a continuous series of stratified rocks, of which the uppermost contain shells and other undoubted characteristics of their rank in the order of rocks.
The extent of this rock on the shore is not great, but it may be seen occupying a continuous line both on the shore of the sound of Soa and within the entrance of Loch Scavig, forming the foot of Garsven, one of the highest of the Cuchullin group.
These are the only places in which I have found this rock, and I have no great reason to expect that it will be found any where else, as its dip does not any where indicate its probable re-appearance; yet I should not be surprised were it to come out at Loch Sligachan, since the limestone which immediately follows it in regular order is to be seen there. These beds, the limestone on the one hand and the quartz with schist on the other, will be guides to these who wish to search for this rock in other parts of the island.
The mineral character of this sandstone is very uniform; it is most commonly of a red colour, but it becomes brown or grayish, when in the neighbourhood of the schist, and sometimes even partakes of the blue colour of this substance. It is of a moderately fine grain and very tractable as a building stone, sometimes possessing the softness of an ordinary sandstone and at others acquiring a flinty kind of hardness, more particularly when it approaches the schist. It is generally mixed with clay, or is of an argillaceous nature, and in some places moreover it is found to contain particles of calcareous matter: in some few places coarser portions are to be
