XIII. On the Junction of Trap and Sandstone, at Stirling Castle.
By J. Mac Culloch, M.D. Chemist to the Ordnance, and Lecturer on Chemistry at the Royal Military Academy at Woolwich.
V. Pr. Geo. Soc.
I have herewith transmitted a sketch of one of those circumstances in the mutual relation of greenstone and sandstone, from which the Huttonian theory is presumed by its advocates to derive so material a support. The particular instance, of which this sketch is intended to give a general notion, has been lately brought to light, and has not, as far as I know, been observed by the geologists of Edinburgh. It does not indeed differ so greatly from the same class of facts in the neighbourhood of that city, as to require very particular attention; but I have been induced to preserve this notice, and drawings of it, (Pl. 12, 13) partly on account of its decided and clear disposition, and partly, lest the same operations by which it was first exposed, may, at no distant period, again remove or overwhelm it. Nevertheless, it may have its use in extending the analogy between those classes of rocks in which this appearance is found, and in rendering it probable that the same cause, whatever it was, presided at the formation of all similar phenomena.
The rock on which Stirling Castle is built, and on which the town also is founded, resembles so strongly that on which Edinburgh stands, that it would be superfluous to describe it very particularly.