18 
a fairly definite epoch. And to us in this part of England itis a 
familiar formation, devoid of the dimness and strangeress con- 
nected with more distant periods such as are illustrated by the 
rocks in Scotland or the extreme west of Englan!. Let us com- 
mences then with the Chalk age. 
It is I suppose hardly necessary to point out to you that chalk 
is a marine deposit, full of sponges, fish remains, and shells of 
molluscs, from which its history is easily extracted. What and 
where was Great Britain in those days? Since the chalk is a deep 
sea formation, if we trace out the chalk deposits in England we can 
tell at least what parts were covered with sea in those far-off times. 
Note then how the chalk occurs in our island. We have our own 
local range of the North Downs reaching from our cliffs as far to 
the west as Salisbury Plain. Nearby parallel runs the range of 
the South Downs from Beachy Head to the same place. A _ short 
spur extends south into Dorsetshire, and disconnected outliers are 
found in Devonshire. A great escarpment runs from Salisbury 
Plain, north-east to the Wash, re appears in Lincolnshire, and 
again in Yorkshire, terminatng in Flamboro’ Head. Then un- 
doubtedly all those districts were under the sea in Chalk times. 
But we cannot limit the submergence to those parts; if what are 
now hills formed the bed of the sea so did the lower lying districts 
between these ranges occupy a similar position, and further, they 
must have been covered with the same deposit of chalk, which has 
since been removed by various natural agencies. 
But now we also find chalk in Ireland in the County of Antrim, 
and again on the West of Scotland in the island of Mull, and in 
the district of Morvern in Argyleshire. The sea must thus have 
extended at least to those parts, how much farther it is not easy to 
say. 
ee us try to realize the physical condition in which our islands 
then lay. There was certainly no island corresponding to what we 
call Great Britain. Whatever of land there may have been before 
then, geologists are pretty certain of the foll »wiag facts :—the 
whole of what is now the eastern and central parts of England 
gradually sank, the slope being as at present towards the east, and 
the eastern waters (where the North Sea is now) slowly encroached 
upon it. First the Lower Greensand was laid down, then the 
Gault, and as the depression went on, the Upper Greensand, not 
evenly everywhere, in some places not at all, for the depression 
was not necessarily uniform, and the high grounds were of course 
the last to be submerged. Still the sinking continued until this 
old sea washed the feet of the Welsh Mountains, reached into 
Devonshire, and stretched north-west across to Ireland, and along 
the west of Scotland, Then the highest parts of Wales became 
