THE CAEBONIFEEOUS FOEMATIONS OF THE BEITISH ISLES. 497 



In the I^orth of England the same system of rocks is often 

 classified thus : — 



((c). Upper measures. 

 (b). Middle measures. 

 (a). Lower measures. 



2. Millstone Grit. 



3. Yoredale Eocks (Upper Limestone-shales). 



4. Carboniferous, Mountain, or Scar Limestone. 



5. Lower Limestone-shales. 



The Coal-measures and the Millstone Grit of the two countries 

 may be regarded as equivalent, though the " Upper red beds (6) " 

 of Scotland are absent in the N.E. of England. 



The Carboniferous Limestone series of Scotland and the Yoredale 

 Eocks of England are, in part, parallel deposits, but not wholly, for 

 the base of the former series, when traced southwards across the 

 border into jN'orthumberland, has part of the Yoredales beneath it *. 

 Hence it follows that the lower portion of the Yoredale Rocks is 

 parallel with the upper portion of the Calciferous Sandstones, and 

 that the Scar Limestone and Lower Limestone-shale are more or less 

 equivalent to the main portion of the same series. 



But the term Yoredale scarcely applies in J^orthumberland, and 

 the Geological Surveyors group the whole of the rocks below the 

 Millstone Grit as the " Carboniferous Limestone Series " in the maps 

 of that county. The upper portion of this group, occupying the 

 position of the Yoredales, is very difi'erent in character from and much 

 thicker than the latter, as seen in their typical development in York- 

 shire ; and the lower portion of the group, more or less equivalent 

 to the Scar Limestone, is virtually a slightly modified southward 

 extension of the Calciferous Sandstones of Scotland. This fact had 

 been noticed by other observers before the official survey of jS"orth- 

 umberland ; perhaps first by our old friend the late Mr. George 

 Tate, of Alnwick, who proposed the following subdivision of this 

 portion of the series t : — 



Calcareous group. 

 Carbonaceous group. 

 Tuedian beds. 



Prof. Lebour J has suggested a modification of this classification by 

 including Tate's Calcareous and Carbonaceous groups in one division 

 under the name " Bernician," the term Tuedian being retained by 

 him for the lowest member of the series. 



Mr. Hugh Miller, in the ' Encyclopaedia Britannica,' adopts and 

 elaborates Mr. George Tate's scheme of arrangement. "We are 



* We owe this information to the officers of the Geological Survey of Scot- 

 land. 



t • History of Alnwick,' vol. ii. p. 444 (1869) ; Nat. Hist. Trans. Northumb. 

 and Durham, 1876, pp. 8 & 9 ; and Proceed. Berwicksh. Nat. Club, vol. iv. 

 p. 151, and vol. x. p. 315. 



X ' Outhnes of the Geolog>' of Northumberland,' 8vo, 1878. 



