(always with the exception of whin dykes) in contact with syenite; this contact can be distinguished in many places at the surface, and it has moreover been brought to light in the excavations which have been formed at the marble quarries; it is so intricate that the limestone is often divided into insulated portions surrounded by syenite, and were it not for the clue which is given by the shores at Kilbride the whole tract is so obscure that it would have remained as unintelligible to me now as it did in the first examination which I made of it. It is too speculative an inquiry to consider what influence the syenite may have had in producing this irregularity; nay I have not even the means of proving that the syenite is posterior to the stratified rocks; but in the course of examining that rock hereafter, I shall assign reasons for supposing that this is really the case, and that like the trap rocks to which it is associated it is not improbably the cause of all the irregularity apparent in this place.
If even the shadow of a doubt could remain respecting the connection of this, which I shall distinguish by the name of the marble limestone, with the shell limestone, it is removed by the discovery of a regular alternation of the two near the farm of Borrereg, a sketch of which (Pl. 2. fig. 2.) is introduced into one of the sections designed for the illustration of these rocks.
The limestone having completely lost all semblance of stratification where it is involved among the syenite, is found forming large insulated lumps, of which the great structure and general fracture resemble that of the Devonshire insulated limestones, and those of Assynt which I have described in the Geological Transactions, vol. 2. It is fissured in various directions, and can be raised in large irregular blocks only. Hence it has very naturally been considered as a primary limestone, an error into which I was at first inclined to
