104. = Prof. Edw. Hull—Submergence of the British Isles. 
different stages of this sheared rock recur at intervals according to 
their position in the plications where they have suffered greater or 
less pressure. 
The dolomite crystals most probably owe their origin to percolating 
water charged with salts of magnesia derived from the surrounding 
shales; and perhaps, in the case of the coral limestone, from the 
corals themselves, as a small quantity of magnesia is often present 
in the corallum. 
Besides forming the intercalated beds of sandstone, silica is 
abundant in the limestones and clay-slates in the form of minute 
quartz-grains and crystals; and these would readily dissolve and 
re-crystallize during and after the processes of contortion and shear- 
ing, as is seen in the replacement and fringing of the oolitic grains. 
It is interesting to note the close association of the oolitic granules 
in these beds with masses of the old reef-forming corals, an associa- 
tion similar to that found at the present time in tropical areas. 
The patches of limestone in the shales undoubtedly owe their 
lenticular form to the forces which produced the shearing ; but on 
account of the superior hardness of the limestone the surrounding 
shales have suffered more in being squeezed out of position, and 
have been altered into tale on the surfaces of the mass. 
In concluding these notes it remains for me to express my obliga- 
tions and thanks to Professor Judd, F.R.S., for his kind and valuable 
advice; to Professor Thorpe, F.R.S., for his kindness in supplying 
me with the analysis of the dolomitic limestone; and to my brother, 
Mr. R. 8. Chapman, for his skill in producing the photographs from 
which the plate has been made. 
EXPLANATION OF PLATE VY. 
Fic. 1.—Oolitic limestone of Devonian age, practically unaffected by pressure, 
from Sampson’s Cave. x 14. 
Fie. 1a.—The same rock treated with acid to show the siliceous portion. x 14. 
Fic. 2.—Oolitic limestone with incipient cleavage, from Watermouth Cave. x 14. 
Fie. 3.—Sheared and dolomitized oolitic limestone, from Rillage Point. x 14. 
Fic. 4.—Extreme condition of sheared oolitic limestone, with ‘‘eyes’’ of calcite, 
and dolomite, from Rillage Point. x 14. 
Fic. 4a.—A portion of the same more highly magnified, to show the dolomite 
crystals with their centres occupied by ferruginous material. 36. 
Fie. 5.—Sheared limestone formed of encrinite remains and oolitic grains; the 
ossicles and stem-joints of the encrinites are almost unaffected by the 
shearing forces. From Rillage Point. x 14. 
Fie. 6.—Sheared coral limestone, from Watermouth. x 4. 
IJ].—Tue Susmercence or tHe British IsheEs DURING THE 
GuactaL Prrtiop. 
By Prof. Epwarp Hut, LL.D., F.R.S., F.G.S. 
HE question of the submergence of the British Isles during, at least, 
one stage of the Glacial period, is deserving of careful considera- 
tion by geologists. Until the visit of the late lamented Prof. Carvill 
Lewis to this country, no one, as far as I am aware, questioned the 
view that the British Isles have been submerged to a depth, in 
some places, amounting to 1300 or 1400 feet—this being the level 
at which shell-beds are found in some parts of England, Wales, and 
