ANNIVERSARY ADDRESS OE THE DRESIDENT. 191 



but that it consists only of two great divisions — a lower, passing down 

 conformably into the Upper Silurian shales, and an upper, graduating 

 upward into the Lower Carboniferous sandstones, with a complete 

 discordance between the two series. 



Prof. Geikie in his memoir traces the series of changes in the 

 physical geography of "Western Europe which took place between 

 the close of the Upper Silurian and the commencement of the Car- 

 boniferous period. Viewed in a large sense the Old Eed Sandstone 

 of Great Britain groups itself stratigraphically into two divisions, 

 physically and palaeontologically distinct, a lower and an upper. 



Prof. Geikie regards the Old Eed as a great lacustrine accumula- 

 tion, and treats of the separate basins of deposit as lakes, to which 

 he has assigned different names : — 



1. Lake Orcadie. — "Embracing all the Old Eed Sandstone to the 



north of the Grampian range, including all the Orkney 

 Islands." 



2. Lake Caledonia or the Mid-Scottish Basin. — " Occupying the 



central valley of Scotland between the range of the High- 

 land mountains on the north and that of the Silurian 

 pastoral uplands of the southern counties. This basin was 

 probably prolonged across the Firth of Clyde into the north 

 of Ireland." 



3. Lake Cheviot. — " A portion of the south-east of Scotland and 



the north of England, extending from near St. Abb's Head 

 south-west along the base of the Silurian hills to the head of 

 Liddesdale, and including the area of the Cheviot Hills." 



4. The Welsh Lake.—" The Old Eed Sandstone region of Wales, 



bounded on the north and west by the Cambrian and Silu- 

 rian rising grounds, but its eastern and southern extension 

 obscured by later formations." 



5. Lake of Lome. — " A district in the North of Argyllshire ex- 



tending from the south-east of Mall to Loch Awe, and 

 perhaps northward up the line of the great Glen." 



At p. 374 of his memoir Mr. Geikie gives the order of succession 

 among the strata, the thickness, and typical localities of the Old Eed of 

 Caithness, which he makes 16,200 feet thick, and then treats of all 

 the subdivisions separately. Pp. 406-414 treat of the Orkney 

 Islands palseontologically and physically; and pp. 414-421 of 

 the Shetland Islands in the same manner. The description of the 

 Basin of the northern Eirths occupies 26 pages. 



I commend this great addition and acquisition to the history of 

 the Old Eed Sandstone of Scotland to every student of geology. 



Professor Hull has lately ably discussed the vexed question of 

 the geological relations of the rocks of the south of Ireland to those 

 of North Devon and other British and continental districts *. 



Mr. Hull had previously discussed, in his paper upon the Dingle 

 beds and Glengariff grits and slates f, the relations of the Upper 



* Quart. Journ. Geol. Soc. vol. xxxvi. pp. 255-276 (1880). 

 t Quart. Journ. Geol. Soc. vol. xxxv. pp. 699-723. 



