118 N'otices of Memoirs — Hugh Miller — Carboniferous Series. 



Tate's classification may be summarized as in tlie following 

 table : — 



Carboniferous Limestone Series of North Northumberland : Tate's 



Classification, 1856-1868. 

 [References : — G. Tate, History of Berwickshire, Naturalists' Club, 1856, p. 219 ; 

 Ihid. vol. V. 1866-7, pp. 283, 357 ; Hist, of Alnwick, 1866, p. 444 ; Tyneside Transac- 

 tions, vol. ii. 1868, p. 6.] 



Upper or Calcareous group: — From the base of the Millstone Grit to the Dun 

 Limestone —" the lowest limestone of any value." Good workable limestones, 

 interstratified among alternations of sandstone, sbale, and coal ; large numbers 

 of marine organisms connected with the calcareous strata. Thickness, 

 about 1700 feet. 

 Lower or Carbonaceous group -.—From the base of the Dun Limestone to the top of 

 the Tuedian group. Marked by the number, thickness, and quality of its coal- 

 seams; limestones thin and generally impure; marine organisms in fewer 

 numbers. Thickness, 900 feet. 

 Tuedian Groups: — Beds intermediate between the Productaland Encrinifal limestones 

 and the Upper Old Red Sandstone. Distinguished by coloured shales, by 

 thin, argillaceous and cherty or magnesian limestone, and by the rarity of 

 of Encrinites and Brachiopoda ; some Stigmarian layers, but no beds of coal. 

 Thickness, about 1000 feet. In one of his papers Tate distinguishes an 

 upper group of " Tuedian grits." 

 [_Upper Old Red Sandstone. Local conglomerates, " more connected with the 

 Carboniferous than with the Devonian." No StigmariaJ] 



The southern part of Northumberland Tate seems to have visited 

 only very occasionally ; but from his small map of the county, 

 in which he uses three colours for his three divisions throughout 

 (Tyneside Transactions, vol. ii.), and from his treatise upon the 

 geology of the Eoraan Wall (Bruce's Eoman Wall, ith edition), 

 it is evident that his careful eye detected nothing to conflict with 

 his classification. Mr. Tate died in lb73. 



In 1875, Tate's classification of the upper divisions of the series 

 was set aside by Professor Lebour in favour of an arrangement 

 more " natural and convenient." Professor Lebour abolished the 

 distinction between the Calcareous and Carbonaceous groups, and 

 threw them together — along with some of the Tuedian grits — into 

 a single large seines, to which he applied the term Bernician. 

 It is based on the assumption that Tate's two divisions either do not 

 exist in nature or do not persist throughout the county. 



Carboniferous Limestone Series in Northumberland: Lebour's 

 Classification, 1875-1886. 



[References: — G. A. Lebour, " On the Larger Divisions of the Carboniferous Rocks 

 in Northumberland," Trans. N. of England Min. Inst. 1876 ; " On the terms 

 Bernician and Tuedian," Geol. Mag. 1877, p. 19 ; " Outlines of the Geology of 

 Northumberland," Newcastle, 1878 ; " Sketch of the Geology of Northumberland," 

 Geologists' Association, 1886.] 



Bernician A large group — which " cannot be divided in any natural 



manner " — of limestones, grits and sandstones, shales, 

 and coals ; lower limit, "a variable one," not keeping to 

 any one horizon; thickness, in North Northumberland, 

 2600 feet (after Tate); in Mid Northumberland, a 

 maximum of " at least 8000 feet " ; in South North- 

 umberland, 2500 feet (after Westgarth Foster j. 



Tuedian As in Tate's classification, but without definition at its 



upper limit. 



Basement Conglomerates Local. 



It has never been contended, the author believes, that Tate's prior 

 classification is not applicable to North Northumberland. It is now, 

 as the result of the labours of the Geological Survey shows, found to 



