Prof. Morns — Lead-mines of the North of England. 319 



Kettlewell and near Malham, to Lancaster, separates, according to 

 Phillips, the Yorkshire Limestone tract into two well-contrasted 

 parts, — the southern type, in which the Lower Limestone Group is 

 nearly undivided, and the Upper Limestone Group thin, and with in- 

 terbedded shales. In the northern type the Lower Limestone Group 

 is divided by shales, sandstones, &c. ; and the Upper Limestone 

 Group, about 1000 feet thick, is complicated, and consists of lime- 

 stone, coal, flagstone, and shales, alternating with each other. In 

 the more northern counties a still greater complexity is observed, as 

 in Northumberland, Durham, and Cumberland, showing a transition 

 to the Scottish type. Thus, north of the Tyne and the great 90 

 fathom dyke, the Carboniferous Limestone is divided by Mr. Tate 

 into two series — the Lower Carbonaceous, the UjDper Calcareous, the 

 total thickness being about 2600 feet, of which 1400 are sandstone, 

 900 shale, 230 limestone, 70 coal ; the lower, about 900 feet, extends 

 from the Tuedian to the Dun limestone, contains little limestone 

 (about 20ft.), but eight seams of good workable coal, of which the 

 Scremerston and Cooper Eye coals are the best. The Upper series, 

 1700 feet thick, is distinguished by its workable limestone (about 

 200 feet thick), interstratified with sandstone, shale, and coal, some 

 of fair quality, as the Shilbottle and Licker coals, and" the Beadnell 

 about 5 feet thick, but others poor and thin. South of the Stublick 

 dyke the whole series, according to Forster's section, has a thickness 

 of 2080 feet, of which 820 are siliceous, 790 argillaceous, and 470 

 calcareous. The series has been divided into two groups, the lower, 

 below the Whin Sill, comprises the Scar Limestone series of Phil- 

 lips, crops out in Cumberland and Westmoreland, and includes the 

 Melmerby limestone. The Upper, comprising the Yoredale series, 

 includes the strata between the Whin Sill and the Fell Top limestone, 

 of which the larger portion consists of argillaceous and siliceous sedi- 

 ments, with about 180 feet of calcareous strata, and 4 feet only of coal. 

 The following table of the relative thickness of the Lead Measures 

 (Yoredale series, Phillips) from the Fell Top Limestone to the Tyne 

 Bottom Limestone above the Whin Sill, shows the principal mineral 

 characters and their alternation, and the predominance of mechani- 

 cally formed over chemically and organically formed strata, arranged 

 from W. Forster's " Section of the Strata," p. 165 et seq: — 



ARGILLACEOUS AND ARENACEOUS. CALCAREOUS. 



FEKT Fell Top Limestone 4i 



Crow Coal, Hazle, Plate, Slate Sill, * 



Firestone, Pattinson's Sill 330 



Plate and impure Coal 68 



Tuft, Hazle, and Plate Beds 102 



Hazle and Plate ., 64 



Hazle and Plate 46 



Coal, Plate, and Hazel 30 



Little Limestone 3 



Tumbler Bed and Great Limestone, 



■with thj.-ee flat veins ... , 63 



Four-fathom Limestone 24 



Three-yards Limestone 9 



Five-yards Limestone ... 6 



