PROCEEDINGS OF GEOLOGICAL SOCIETIES. 



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The banks of the stream which winds through the glen exhibited various 

 sections of strata consisting chiefly of sandstones and impure limestones ; and 

 on arriving at a steep bank of shale containing narrow bands of the latter rock, 

 one of the vice-presidents called the attention of the party to the circumstance 

 that these deposits rested upon Old Red Sandstone, which appeared in the bed 

 of the stream, and were evidently the lowest members of the Carboniferous 

 system in the district ; at the same time remarking the strong resemblance these 

 thin-bedded strata presented to the "Ballagan beds," immediately succeeding 

 the Old Red Sandstone of the Strathblane and Campsie districts, so well 

 described by Mr. Young in the first number of this Society's Transactions. 

 In one part of the " gill" an extensive fault was observed, crossing the stream 

 at right angles, producing a vertical displacement of the strata to the extent, 

 probably, of one hundred and twenty fathoms, so that there is a sudden transi- 

 tion from the Old Red Sandstone to the Coal measures, with their characteristic 

 organic remains. Further down the stream.a thick bed of limestone, containing 

 Product us giganteus, indicates the base of the Carboniferous system, and a 

 relative depth of nearly four hundred fathoms below the " ell coal," which 

 occupies a position near the upper stage of the Lanarkshire coal-field. They 

 then took the shortest route to Crossford, where the Xethan Water unites with 

 the Clyde. Here they were joined by Laird Templeton, an enthusiastic local 

 geologist, who led the way up the valley of the Xethan. On either side of the 

 river fine sections presented themselves, and it soon became apparent that the 

 rocks to be examined were chiefly of marine limestones and clay ironstones, 

 with shales and sandstones, some of the deposits being evidently of estuary 

 origin, and in all likelihood equivalents of the strata in the neighbourhood o£* 

 Lennoxtown, on the north-west margin of the great coal basin. The only 

 igneous products observed were some rolled fragments of a light-coloured fei- 

 stone porphyry in the bed of the stream, with a similar ruck used as road metal, 

 indicating a trap-area at no great distance. In the lower part of the Xethan 

 hills the strata formed precipitous banks, at one point attaining an elevation of 

 about three hundred feet above the bed of the stream — a fault causing a down- 

 throw to the extent of several fathoms. Further up the river an exhausted 

 opencast coal-pit was observed. Doubts were soon removed as to the true 

 position of the strata, for before long the fossils of the Lower Limestone series 

 presented themselves in the form of various Brachiopoda, the Lingula iron- 

 stone indicating a higher stratigraphical order than the Productus limestone of 

 the Braid wood gill. Under a projecting mass of strata a fire was kindled from 

 coal supplied by a seam on the spot, and coffee was prepared and served out to 

 the willing recipients, who had been under the necessity of making considerable 

 exertion in threading their way among the numerous blocks of stone strewn on 

 the banks of the stream. At the base of the lofty eminence on which 

 Craignethan castle stands, a bed of .shale was pointed out by Mr. Templeton as 

 containing numerous fossils ; and here the party left the course of the river in 

 order to visit the famous archetype of Sir Walter Scott's castle of Tillietudlem. 

 A great portion of the edifice has been removed to build the neighbouring farm 

 houses ; but two towers still remain, with part of a solid wall of hewn stone 

 perforated with loop-holes. From the commanding position, the prospect was 

 interesting in the extreme. Round the base of the cliff on which the castle 

 stands winds the X T ethan, fringed with leafy verdure, and away in the distance 

 beyond an undulating district the eye could embrace the south-eastern limit of 

 the great coal-field of Scotland. The excursionists then retraced their steps, 

 and on returning to Crossford examined Laird Templeton' s collection. 



VOL. IV. 



