1862.] HTTLL CAEBONIFEEOTJS STEATA. 14l 



greater than that of North Staffordshire by 2200 feet, and of War-^ 

 wickshire by 8750 feet*. 



Ciimhet^land. — It might have been expected, according to the 

 principle of north-westerly expansion which I am now endeavouring 

 to explain, that the sedimentary series of Cumberland should be 

 even thicker than that of Lancashire, lying, as it does, to the north 

 of this latter county. This, however, is not the case ; and to account 

 for the meagre development of the Carboniferous rocks there appeared 

 to me for some time extremely difficult. I feel confident, however, 

 it is only an apparent anomaly, and is capable of explanation. The 

 proximity of the Cumbrian Mountains is evidently the primary cause 

 of the thinness of the strata ; and my friend, Mr. Salter, has sug- 

 gested to me that a shallow sea and a shelving shore are sufficient 

 to account for these phenomena. There is at least another explana- 

 tion, and that is, that the Cumbrian Mountains having been islands 

 in the Carboniferous sea, and rising in front of the current which 

 brought the sediment, caused it to bend from its course, and by in- 

 creasing the velocity, prevented the deposition of the full supply near 

 their coasts. Either of these explanations appears sufficient. 



Scotland. — From the position of the Carboniferous rocks which 

 occupy the great depression between the Eirths of Eorth and Clyde, 

 as compared vrith their representatives south of the border, and 

 from the substitution of stratified shales, sandstones, &c., for lime- 

 stones in the lower portion, it seems probable that, when the whole 

 series was originally deposited, the sedimentary portion attained 

 a development unsurpassed in any other district in Britain. In 

 reality, however, we have no means of judging of the thickness of 

 the Upper Coal-series, as it is incomplete, a vast quantity of strata 

 having probably been removed by denudation from off the present 

 coal-areas. 



The highest member of the Carboniferous series is the '' Elat- 

 coal Group," representing (as shown by Messrs. Howell and Geikie) 

 a portion of the true Coal-measures of England, as being more recent 

 than the Eoslyn sandstones, the equivalent of the MiUstone-gritf. 

 The thickness of this division is 1000 feet in the Lothians, and 840 

 feet in Lanarkshire, according to Mr. Ealph Moore t- The " Elat- 

 coal Group " would appear from the fossil shells, which consist of 

 various species of Anihracosia, to be the equivalent of the Middle 

 Coal-series of England; and we have hitherto looked in vain for 

 representatives of the Lower Coal-measures, or Gannister Beds, with 

 their peculiar Lower Carboniferous Mollusca. The MiUstone series 

 is then, compared with that of Lancashire or Staffordshire, only 

 1500 feet, as is also the case with the " Edge-coal Group," while 

 the sedimentary strata of the Carboniferous Limestone have enor- 

 mously expanded. It thus appears that there has been an increase 



* Most of these thicknesses have been determined by Mr. Binney, F.R.S., with 

 the exception of the Millstone-grit and Yoredale series, which were partly mea- 

 sured by myself. (See Mr. Binney's papers in Trans. Geol. Soc. of Manchester, 

 vol. i.) 



t " IVfemoir onthe Geology of Edinburgh," p. 105. 1861. X " Vertical Section." 



