300 G. W. Tiirrell— Intrusions of KihyUi-Croy Didrid. 



Eocks of the Firth of Forth, ^ later in his Presidential Address to the 

 Geological Society in 1892," and finallj^ a detailed account has been 

 given by him in his Ancient Volcanoes of Great Britaiti.^ Dr. Teall^ 

 has described rocks from Kilsyth and Croy, Mr. Monckton has 

 described similar rocks from the Stirling district,^ and Dr. Falconer 

 from the Bathgate Hills.« 



II. Steucture of the Kilsyth and Ckoy District. 

 The rocks of this area belong mainly to the Carboniferous Limestone 

 Series. They are bounded by the Millstone Grit on the west, south, 

 and east, and by the Calciferous Sandstone and its intercalated lavas 

 to the north. The boundary here is the main E.-W. fault. The 

 general succession is given below. Only the outstanding horizons of 

 limestone, coal, etc., are given. It must be understood that these 

 are separated from one another sometimes by hundreds of feet of 

 sandstone and shale. 



Millstone Grit = Roslin Sandstone. 

 / Castlecary Limestone. 

 Calmy or Arden Limestone. 

 Bishopbriggs Sandstone, 

 p , .J. Index or Cowgien Limestone. 



Uarboniterous I Biackband Ironstones, Nos. 1-4, with 



Limestone Series. \ ^^.^ ^^^^ ^^ Meiklehill near top. 

 Main Coking Coal of Kilsyth. 

 Hosie's Limestones. 

 Hurlet Limestone. 

 Calciferous Sandstone Series, with intercalated volcanics. 

 The dominant structural feature is the sharp anticline in the 

 Carboniferous Limestone Series, locally known as "The Riggin", 

 which runs in a south-west to north-east direction, from Twechar to 

 Banton. The general strike of the beds is therefore south-west to 

 north-east, but the country is much broken by a series of E.-W. 

 faults, the largest of which brings the Calciferous Sandstone and its 

 volcanics into contact with the Carboniferous Limestone Series to the 

 north of Kilsyth. There is also a set of smaller faults, the general 

 direction of which is from north-west to south-east. In the course of 

 the revision of the district by the Geological Survey it has been 

 shown that the structure of the Riggin is not so simple as formerly 

 supposed, but that there is a series of more or less parallel wave-like 

 troughs and ridges having a general N.E.-S.W. trend." 



III. Geology of the Intrusions. 

 Horizon. — The intrusions are, as a whole, roughly conformable to 

 the bedding, although in places they gradually transgress. The main 



1 T.R.S.E., 1S79, Tol. xxix, p. 505. 



2 Q.J.G.S., 1892, vol. xlvii, proc. 105. 



3 Vol. i, pp. 417-23, 446-61 ; ii, pp. 140-3, 155-8. 

 « Brit. Fetrocj., 1888, p. 192. 



= Proc. Geol. Assoc, 1891-2, vol. xii, p. 242, with petrog. appendix by 

 J. G-. Goodchild; also Q.J.G.S., 1895, vol. li, pp. 480-91. 

 « T.R.S.E., 1905-6, vol. xlv, pt. i, p. 137. 

 "^ Sumni. Prog. Geol. Snrv., 1905, p. 124. 



