270. Paleo-Geological and Geographical Maps of the British Islands. 
- The unconformity between the Upper Devonian Sandstone (or Upper Old Red 
Sandstone), and the Devono-Silurian beds (¢.e. the ‘Dingle beds” of Ireland, and 
the “ Lower Old Red Sandstone” of Scotiand), indicates that after their deposition 
these beds were subjected to disturbances, were elevated into land surfaces, and ex- 
posed to denudation. In this position they remained throughout the Lower and 
Middle Devonian periods, and were only resubmerged when that of the Upper 
Devonian set in. Plate XXVI., Fig. 2, represents the period of elevation of the 
west and north of the British Isles, and of the concurrent depression of the region to 
the south. 
It is probable, also, that the centre and north of France (Normandy, Britany, 
and the Ardennes), were ina condition of land-surfaces during the deposition of 
the Lower and Middle Devonian beds, as these everywhere rest, and with varying 
geological horizons, against the older formations of which this part of France is largely 
formed. We must also recollect that the whole area of the south of the British 
Isles, and of the adjoining parts of the continent, has undergone enormous lateral 
compression, in a north and south direction, owing to which the originally 
horizontal Devonian and Carboniferous beds have been crushed into numerous 
sharp foldings and flexures, lying along approximately east and west axes, and that 
these extend from the extremity of Kerry and Cork through Devonshire, under the 
‘Thames valley, and reappear in France and Belgium, and as far as the banks of the 
Rhine. 
If, therefore, we wish to realize the geographical position of the Devonian beds 
as originally deposited, we must reduce these flexures of the beds to the horizontal 
position, in which case the present apparently narrow trough running across the 
south of England and north of France would be spread out to probably almost 
twice its present width.* 
Distribution of Land and Sea.—On the above grounds, therefore, I have repre- 
sented in Figure 2, the whole of the western and northern portions of the British 
Islands, with the adjoining portions now covered by the ocean, as land during the 
Middle Devonian period. Contemporaneously with this the sea extended over the 
south of England, and eastwards into Germany, under the waters of which were 
deposited in England the fossiliferous limestones of Ilfracombe and Plymouth ; in 
Belgium, the “ Calcaire de Givet ;’ and in Germany, the ‘“ Stringocephalus lime- 
stone.” Once we thoroughly understand the physical relations of these different 
areas, the reasons for the present distribution of strata become clear. 
* The flexuring of these beds, as laid open along the Meuse, is very well shown by M. Gosselet in a 
drawing, as copied by Dr. Mourlon, in the “Géol. de la Belgique,” t. 1, p. 56. As the average angle of 
inclination exceeds 45°, the original length would have been in this case more than twice the present. 
