1852.] SEDGWICK ON THE LOWER PALEOZOIC ROCKS. 141 



4. Upper Cumbrian group. (1.) Great stratified contemporaneous 



masses of porphyry, trappean conglomerates cemented by fel- 

 stone-porphyry, trappean shales {schaalstein) — all frequently 

 alternating with great beds both of coarse and fine chloritic 

 slate ; altogether of enormous thickness. 



(2.) Coniston limestone and calcareous slate ; partly interlaced with 

 the top beds of the preceding. Thickness 200 or 300 feet. 



(3.) Coniston flagstone ; in its upper beds containing here and 

 there some thin calcareous bands. Thickness about 1500 feet. 

 Of these three sub-groups, (1) represents the lower Cambrian 

 rocks of N. Wales ; (2) and (3) represent the Bala limestone 

 and the beds over it ; and therefore represent, though on a 

 rather degenerate scale, the upper Cambrian groups of North 

 and South Wales. 



5. Coniston grits. Thickness variable ; on the average, not perhaps 



less than 1500 feet. The exact equivalent of the Caradoc sand- 

 stone — the lowest group of which the true relations are made out 

 in the sections of the 'Silurian System.' 



6. Ireleth slates; composed, in the ascending order, of — (1.) Dark 



calcareous slates. (2.) Calcareous slates with concretionary bands 

 of limestone. (3.) Upper Ireleth slates. Collectively of great 

 thickness ; and the n^ar equivalents of the Wenlock shale and 

 limestone. 



7. Coarse slate, flags, grits, ^c. ; not physically well separated from 



the preceding group of Ireleth slates ; but higher in the section, 

 and therefore approximately the equivalents of the lower Lud- 

 low rocks, and of great thickness. 



8. Rocks of Kirkby Moor. The highest group of the series. Fine and, 



coarse flagstone, coarse bands of slate, grits, red flagstone, &c. 

 It is the equivalent of the upper Ludlow rocks and Tilestone, 

 and abounds in upper Ludlow fossils. 



9. Old red sandstone. 



10. Carboniferous limestone. 



This arrangement may be more clearly shown in the accompany- 

 ing table : — 



Palaeozoic Rocks of Cumbria. 



Carboniferous Limestone. 



Old Red Sandstone. ft.* 



f Flags and grits of Kirkby Moor 800 = Upper Ludlow. 



Coarse contorted slate and gritstone 800 = Lower Ludlow. 



Silurian J f Upper Ireleth slates 500"] 



Series. 1 Ireleth slates. <| Lower Ireleth f Calcareous slates 80 [■ = Wenlock group. 

 [ slates. \ Dark slates... 200 J 



[^Coniston grit 2000 = Caradoc sandstone. 



r Coniston flagstone 1500 "1 = Upper Cambrian (Bala, 



/TT r. u • \ Coniston limestone 300 J &c.) of N. Wales. 



(Upper Cu.bnao.) | ^^^^^^ ^^^ ^^^^^ ^^_^^^ ^ -^"^^^^^ "' '^^ 



^ (Lower Cumbrian.) Skiddaw slates 6000 



Metamorphic slates. 

 Granite. 



* These are given merely as approximate measurements. 



Cambrian 

 Series. 



