SIMPSON : STRATA AND DEPOSITION OF THE MILLSTONE GRITS. 415 
land and water areas, that must have taken place about the close of 
the Yoredale period. In a physical history of the Carboniferous 
period the Grit series would necessitate a new chapter, as I think 
there is strong evidence in support of the theory that they were laid 
down under somewhat different conditions from the preceding Yore- 
dale group. Several eminent geologists have described the probable 
physical and geographical features of this period, and although there 
are naturally differences of opinion as to special land and water 
areas, there is sufficient general agreement to justify us in taking 
their geographical restorations as on the whole] warranted by the 
data obtainable. 
Jukes-Browne in his " Building of the British Isles," publishes a 
map covering the present British area, showing the probable relations 
of land and water of the Carboniferous period, and in the light of 
what is known up to the present, we may take it asjprobably the best 
that can be done. 
He shows a large continental area to the north, embracing parts 
of the West and North of Ireland, stretching in a north-easterly 
direction across the middle of Scotland, until it joins a considerable 
prolongation of the present Scandinavia, an extension of that country 
stretching, with probably several important bays, down the present 
North Sea area, almost to our eastern coast of to-day, and with its 
southern coast line running easterly at about the latitude of our 
present Humber. 
In the south, land is shown about a hundred miles south of 
Ireland, taking in part of Cornwall and stretching across to Brittany. 
These continental areas partially enclose a sea, which, with the 
exception of a large central and sundry smaller islands, covers the 
whole of England, the southern half of Scotland, and the whole of 
central and southern Ireland. 
The large island in the middle of this Carboniferous sea is roughly 
L-shaped, with its longer north and south axis stretching from the 
Mull of Galloway to Pembrokeshire, embracing parts of the east 
coast of Ireland, the north of the Isle of Man, a small portion of 
Anglesea, and practically almost the whole of the western and southern 
portions of the Irish Sea ; the eastern prolongation takes in a good 
