ALTERED LIMESTONE OF STRATH, SKYE. 65 



ground made very natural. Without pleading for the existence of 

 any such confusion in the interior as Maculloch's exaggerated 

 language would lead one to expect, I think the occurrence of a 

 group of limestones on both the east and the west coast of the island 

 would predispose any observer to take the limestone of the inter- 

 vening inland district for part of the same series. This obvious 

 inference is strengthened by the first examination of the coast- 

 sections. At Broadford, for instance, the limestones, which else- 

 where dip seaward at gentle angles, are found between the harbour 

 and the bridge to be thrown into highly inclined positions and to 

 strike straight for the interior, where after a short concealed space, 

 the massive or so-called " unstratified " limestone makes its appear- 

 ance. Then, on the opposite side, the shore of Loch Slapin, south- 

 west of Kilbride, displays an admirable section, where the two 

 limestones are actually in contact. I shall describe this section in 

 a later part of the present paper, and will only remark here that 

 unless one's suspicions were aroused to look out for a break between 

 these limestones, no such break would probably be noticed even by 

 a tolerably alert observer. All that would be likely at first to 

 engage his attention would be the transition from an overlying well- 

 bedded group of limestones full of Gryjphcea and with thin shaly 

 partings, into a lower group of more massive limestones with no 

 Gryphoia and no layers of shale. If he were told that the seeming 

 gradation conceals so vast a hiatus as that between Lower Silurian 

 and Lias, he would probably express an emphatic dissent from such 

 a statement. It was this coast-section which chiefly deceived me in 

 my early rambles over the ground, and blinded me to the meaning of 

 other evidence which I could otherwise hardly have failed to recog- 

 nize. And from the importance assigned to it by Macculloch, I 

 imagine that it had the same unfortunate influence upon him. 



§ 1. LiTHOLOGICAL CHARACTERS OF THE LiMESTONE. 



The thin-bedded, dark blue, more or less earthy Lias limestones of 

 the coast-sections, alternating as they do with courses of dark sandy 

 shales and sandstones, present such well-marked lithoiogical charac- 

 ters that even in the midst of much confusion, produced by faults 

 or eruptive rocks, they ought to be easily distinguishable from any 

 other group of strata in the geological structure of Skye. That 

 they stretch across the island from sea to sea, as stated by Macculloch, 

 is indisputable. They can be followed continuously from the eastern 

 shore at Lussa south-westwards, along the escarpments which they 

 form, to the shore of Loch Eishort near Boreraig. But instead of 

 spreading northwards from these escarpments over all the low 

 ground of Strath, as hitherto believed, they form merely a narrow 

 strip averaging about a mile and a half broad, of which the western 

 and northern margin is bounded by a line drawn from a point on 

 Loch Slapin near Camas Malag eastwards to the glen above Boreraig, 

 and thence northwards to near Broadford Mill. The belt of Lias, 

 which at Broadford is not more than half a mile broad, turns west- 



Q. J. G. S. No. 173. F 



