62 PALAEOZOIC TIME. [CHAP. V. 



discoveries in Forfar, affords good ground for concluding 

 that there was no direct communication between the waters 

 of the two lakes. 



There is less evidence for regarding the Cheviot basin as 

 distinct from the Caledonian, as no fish have yet been 

 found in the Cheviot district, and we do not know how far 

 the Lower Old Red originally stretched over the southern 

 uplands ; much of it was removed before and during the 

 formation of the Upper Old Red, the latter in all proba- 

 bility deriving much of its material from the destruction 

 of the older series. The Lower Old Red partakes in the 

 plication of the Silurian and Ordovician rocks of southern 

 Scotland, and it may for ought we know have been co- 

 extensive with them over the whole region. On the other 

 hand, it should be noted that the Lower Old Red of the 

 Cheviot district rests unconformably on the Silurian, 

 which is an unusual relation, and suggests that the 

 Cheviot basin was formed at a somewhat later date than 

 the Caledonian basin by a local depression of the land 

 surface. This, however, is not incompatible with its 

 having then been an inlet or extension of the Caledonian 

 Lake, but I have not ventured to express this view on 

 the map, which is a rendering of Dr. G-eikie's opinion. 



The greater part of Ireland likewise seems to have been 

 land enclosing lake basins, and was doubtless at this time 

 connected with England and Scotland, so that the whole 

 formed one mass of land, and was part of a large con- 

 tinent that extended far westward into the place now 

 occupied by the North Atlantic. The tract of Old Red Sand- 

 stone in Tyrone being in alignment with that of the central 

 Scottish basin, Professor Hull has suggested that the Lake 

 Caledonia extended thus far into Ireland, and I have 

 adopted this view in the restoration of Old Red Sandstone 

 geography (PI. III.). The other small tract of Old Red 

 recently discovered in Donegal may have been formed in a 



