Silurian Rocks of North TJTales, §fc. 101 



only. For if it bo granted, that in Britain the Lower can generally 

 be so separated from the Upper Silurian, as to bo capable of demarca- 

 tion on a map, how could tho geologist succeed in separating the 

 Upper and Lower Silurian of Christiania in Norway, where these 

 groups, each equally well characterised by fossils as in our own coun- 

 try, fold over together in such small united masses \* 



Having stated that the Upper and Lower Silurian roots of Europe, 

 including all the fossiliferous strata of Wales, are so knit together by 

 fossils and the transitions of the masses, that they must be viewed as 

 one natural history series, I will now conclude by simply indicating 

 the small area in various countries to which the Silurian system would 

 be reduced, if the meaning of that term were to bo changed and 

 restricted to the upper half of the original system. 



In England, though prominent in tho typical districts of Shrop- 

 shire and Herefordshire, the Silurian rocks, so dismembered, would 

 occupy a mere band (scarcely to be defined on a general map) in 

 Brecknockshire, Carmarthenshire, and Pembrokeshire ; whilst all 

 the broad and specially typical Lower Silurian tracts laid down by 

 me in Salop, Montgomery, Radnor, and South Wales, must be erased, 

 since it is impossible to distinguish them by their organic remains 

 from the groups of Snowdown. In Ireland, from what we already 

 know, whether through the works of Mr Griffith, Captain Portlock, 

 or the labourers of the Government Surveyors, tho system would 

 pretty nearly disappear, as the great mass of the Irish lower palaeozoic 

 fossils are found to be Lower Silurian. 



In Russia in Europe, and in nearly all Scandinavia, Lower Silu- 

 rian rocks and fossils only prevailing, the very name Silurian would 

 be swept from the map, and the system so attenuated, would there 

 be confined to Gothland and some small Baltic isles I 



Now, it must be borne in mind, that even when the lower and 

 upper groups are united in one system as at present, the Silurian 

 rocks of Russia do not occupy one-fifth part of the area of either 

 the Devonian or Carboniferous systems of those regions,t whilst in 

 Germany, the whole system, as at present united, bears an infinitely 

 small proportion to the overlying Devonian group. A glance at the 

 Geological Map of America, in Mr Lyell's work, shews to what a 

 small area, in relation to the other palaeozoic rock system, the Silu- 

 rian would be reduced, if its lower half were abstracted. 



Independent, therefore, of the impropriety of mutilating a system 

 established on the community of its zoological contents, the results of 

 such an arrangement would be a violation of the meaning which ought 

 in fairness to be attached to a great natural history period, which was 

 typified as such before tho Devonian System was thought of. There 



* See woodcut, Russia in Europe, &c., vol. i., p. 17, and Quarterly Journal 

 Gaol. Society, vol. ii., part 2 (Miscell.), p. 71. 



t See General Map, llussia in Europe, and the Ural Mountains. 



VOL. XLIII. NO. LXXXV. — JULY 1847- L 



