Mineralogy of Sky. 41 



(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 j 

 nay I have not even the means of proving that the syenite is pos- 

 terior to the stratified rocks j 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 (PI. 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 stratifica- 

 tion 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 irregu- 

 lar blocks only. Hence it has very naturally been considered as a 

 primary limestone, an error into which I was at first inclined to 



Vol. hi. f 



