402 Prof. Sedgwick on the New Red Sandstone Series in the 



moulded. But in comparing the unconnected deposits of remote countries^ 

 we must act on an opposite principle ; learning- to suppress all local phaeno- 

 mena, and to seize on those only which are coextensive with the objects we at- 

 tempt to classify. In this general view the arrangement of the red sandstone 

 and carboniferous series in one great group, is perhaps the best fitted to the 

 present state of our knowledge. 



§ 4 . General Comparison of the Red Sandstone Series of Scotland and England. 



It has been shown bv Mr. Murchison and myself, that in the Isle of Arran 

 a carboniferous series is interpolated between two enormous masses of red 

 sandstone and conglomerate ; and that the whole group passes, in the ascend- 

 ing order, into a formation of red sandstone, which mai/ represent either one 

 of the red, sterile parts of the Scotch carboniferous series, or the lowest di- 

 vision of the new red sandstone*. It is almost impossible to ascertain the 

 precise limit of this upper red sandstone of the Isle of Arran : but the best 

 way of approximating to it would be to trace the old red sandstone group 

 from the south flank of the Grampians to the west coast of Scotland; and from 

 thence to follow the red sandstone series to the coasts of Ayrshire. By the 

 help of such an examination (a desideratum in Scottish geology), we might 

 perhaps establish such analogies as would enable us to determine the exact 

 upper limit of the Arran section. 



I consider it now established beyond doubt, that the great masses of red 

 sandstone and conglomerate which fringe the Highland coasts, and range, on 

 the south flank of the Grampians, from one side of Scotland to the other^ 

 belong almost exclusively to the old red sandstone. The large development 

 of the bituminous schist of Caithness has thrown some unnecessary difficulties 

 in the way of this conclusion. It alternates, however, with the old red con- 

 glomerates to their base, and cannot be separated from them'f ; it is overlaid 

 by a red sandstone decidedly of older character than any variety of the new 

 red and variegated group ever seen in other parts of Great Britain ; it con- 

 tains a suite of fossils peculiar to itself; not, as far as is known, interchanging 

 a single species with the magnesian limestone; it is represented (and by no 

 means in an unusual form) on the south flank of the Grampians by a series of 

 thin-bedded strata, placed by Mr. Lyell even lower than the old red sand- 

 stone;]; : and, lastly, the remains of fish have been found by Dr. Fleming in 

 groups of slaty sandstone, which, though superior (like most of the Caithness 

 schists), to the lowest old red conglomerates, are inferior to the true carboni- 



* Geological Transactions, Second Series, vol. iii. p. 21 ; and Plate III. 

 t Ibid. pp. 140. 157. 158. + Ibid. vol. ii. Plate X. 



f 



