THE CARBONIFEROUS 8Y8TKM 207 



has been divided into three groups, the lower portion, which is 

 nearly 6000 feet thick, was undivided. 



According to the late J. ft. Good child 10 the lower portion i- 

 ijiially capable of division into three groups, which he called 

 (1) the Ballagan Beds, (2) the Gran ton and Hailes sandstones, 

 (3) the Oil-shale Group. He regarded the sandstone group as the 

 equivalents of the Fell sandstones and the Oil-shales as corre- 

 sponding with the Carbonaceous division of the Border counties. 

 The Geological Survey has not entirely accepted this nomenclature, 11 

 but has included the massive sandstones in the Oil-shale Group 

 because some thin oil-shales have been found in them. In the 

 following table Goodchild's divisions are adopted as being con- 

 venient and lending themselves to correlation with Northumberland. 



Thtekn-s Scotch Divisions. Northumberland. 



500 /. Upper Limestone Group 1 



800 e. Edge Coal Group j-Yoredale Beds. 



500 d. Lower Limestone Group 



2500 c. Oil-shale Group Carbonaceous Group. 



1500 b. Granton and Hailes sandstones Fell sandstones. 



1300 a. Cement-stone (or Ballagan) Beds Cement-stone Beds. 



Cement-stone Group. In Edinburgh, Linlithgow, and Fife 

 this consists in the lower part of clays, shales, sandstones, and 

 tuffs with some beds of dull compact limestone (cement-stone) and 

 of siliceous sinter ; this part is about 200 feet thick. Next in the 

 Edinburgh district comes the volcanic episode of Arthur's Seat, a 

 set of basaltic lavas and tuft's with interstratified sandstones and 

 shales, having a total thickness of 750 feet. These are covered by 

 the Abbey Hill shales, which are 300 feet thick and contain 

 marine fossils. The fossils in the lower part of the group are 

 diictly plant remains and small freshwater Crustacea (Leperditiu, 

 Estheria, Bythrocypris, etc.), but at Belhaven, near Dunbar, a 

 flattened form of Modiola Macadami occurs in hundreds. 



In the Glasgow district this group has been called the Ballagan 

 Beds, and there it consists entirely of sedimentary deposits, sand- 

 stones, shales, and argillaceous limestones, without any con- 

 temporaneous volcanic rocks, though the thickness is still from 

 1200 to 1500 feet 



Granton and Hailes Sandstones. This group consists 

 of two thick sandstones separated by a band of shales. The lower 

 member is the Granton sandstone, probably about 800 feet thick : 

 the central band consists of the Wardie shales (400 feet), and the 

 upper is the Hailes sandstone, which may be 1000 feet thick. 

 These sandstones form good building stones, but have yielded few 



