185/.] GEIKIE SKYE. 9 



describing under three or four subdivisions those appearances that 

 seem most worthy of consideration in the geology of Strath. The 

 first subject to which I shall advert is the long sandstone-ridge and 

 its accompanying breccia. 



Limestone-breccia. — In detailing the sequence of beds along the 

 north-eastern shore, reference has been made to a bed of limestone- 

 breccia which, though not visible on the coast, can be seen at many 

 places in the interior. This rock and its attendant circumstances 

 appear to have escaped the notice of Macculloch * ; yet it is a point 

 of not a little interest, and throws some important light upon the 

 physical history of the district. Its horizon lies a short way above 

 the thick shale that occurs in the lower portion of the series at 

 Breakish ; and this position it probably always retains. It varies in 

 thickness from 3 or 4 feet to 1 or 1 2, and is made up of rounded and 

 subangular fragments of quartz-rock, red sandstone, and lias-limestone. 



Its line is accurately defined by the eastern edge of a long belt 

 of red sandstone (similar to that whereon the lowest lias-beds re- 

 pose), around which it seems moulded. This narrow strip of sand- 

 stone is bounded on the west by a fault that runs through the valleys 

 of Glen Kilbride, Loch Lonachan, and Glen Shuardail, and is well 

 exposed in the channel of the Shuardail Water, where it gradually 

 dies out before reaching Sculamus. The other edge of the sandstone- 

 belt is fringed by the breccia. Except at one spot on the southern 

 ridge of Glen Kilbride, where, for a short way, there intervenes the 

 lenticular mass of white quartz-rock already noticed, and also on the 

 western slope of Beinn Shuardail, where the breccia is overlapped 

 by limestone, the sandstone is always found to have a capping of 

 breccia ; and, I make no doubt, were the anticlinal ridge of Beinn 

 Shuardail stripped of the limestone by which it is enveloped, the 

 sandstone below would be found girdled by a zone of breccia. The 

 only locality where I have detected the latter rock away from the 

 sandstone is in the bed of the stream that descends from the Black 

 Lochs to Heast. The following sections will explain the structure 

 of that part of Strath. 



The Section through the northern end of Beinn Shuardail (fig. 5) 

 crosses the anticlinal of red sandstone with the flanking breccia and 

 limestones. The breccia probably thins out over the older limestone 

 and shales as here delineated. Had it been continuous, we should 

 have found it at b' above the Breakish-shales. These lower beds 

 must abut against the bottom of the breccia in the manner shown in 

 the section ; for that they cannot pass above the breccia, is proved 

 by the position which it occupies at Heast, and by the limestone- 

 fragments with which it abounds. Assuredly it cannot be on the 

 same horizon with the lower conglomerate found resting on the red 

 sandstone from Lussay to Heast (fig. 4). 



The Section between Beinn na Cham and Hill of Harripool (fig. 6) 

 passes south of the gap in the syenite-range of Beinn na Charn and 



* He does, indeed, mention a calcareous conglomerate next the syenite, but 

 adds that " its connexions cannot be traced." — Description, vol. i. p. 325. 



