cXVl PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 
gain of the sea on the land. The prevalent in-shore wind, while 
blowing at times with considerable force, constantly drives dry sand 
into the harbour, tending to fill it up, the outflow of the tide only 
carrying back to the sea a part of the sand thus blown in; on the 
land side also every fall of ram, forming a temporary flood, leaves 
detritus. As no river now flows out of the harbour, tidal action alone 
(except during the temporary effects of rains) has to contend with 
the causes filling up the space imside the sands, and thus the conti- 
nuation of the mud-flats occurring within the present harbour becomes 
exposed outside to the action of the sea; the sands which for- 
merly protected the mud-flats, while river-action afforded a sufficient 
supply of detritus to be piled up im banks, being driven over the fiats 
inwards. 
Respecting the manner in which mineral matter may have been 
accumulated in former geological times, Mr. Lycett, describmg the 
great oolite as it occurs in the neighbourhood of Minchinhampton, 
observes that even a cursory glance at the sections.of that vicinity 
show the beds to have been accumulated in a shallow sea, where strong 
currents prevailed, the surface and mineral character of the deposit 
continually changing. ‘“ Heaps of broken shells,” he adds, ‘ piled 
i uncertain laminated beds, are intermixed with occasional rounded 
fragments of rock, (foreign to the neighbourhood,) of abraded ma- 
drepores, dicotyledonous wood, crabs’-claws, &c.’’ He further re- 
marks upon the apparent denudation of some shelly beds, the cavities 
left by the removed portion being filled with clay, on the common 
false bedding, on the non-conformity of certain beds in juxtaposition, 
and upon the barren or less fossiliferous character of other beds. 
He gives avery detailed account-of the beds he describes under the 
head of the compound great oolite, included in a thickness of about 
130 feet, not neglecting their very changeful character. This deserip- 
tion constitutes a valuable addition to our information respecting the 
local mineral structure of a part of the oolitic series, which, taken 
as a whole, in its range from the coast of Yorkshire to that of Dor- 
setshire, affords a most excellent opportunity for the study, over a 
limited area, of modifications and changes im physical conditions 
during the lapse of a certain portion of geological time. No doubt 
parts of these deposits have been so removed by denudation that we 
lose their contact with the older accumulations which bounded them 
in one direction; and, on the other hand, they are so covered up 
by more modern deposits, that a stripe only remains of the old 
oolitic area. Enough, however, is still exposed to reward examina- 
tion; and a careful comparison of its mimeral character, with the 
mode in which mineral matter is accumulated at the present day, will 
be found highly instructive, more particularly if we extend our view 
to those other parts of Europe where deposits of equal date may be 
exposed. We have elsewhere endeavoured to point out the modifica- 
tions observable in the lower part of the oolitic series, when the Men- 
dip Hills in Somersetshire, and other places extendmg imto South 
Wales, im all probability, after formimg islands and shores, were so 
depressed beneath the sea-level as to be covered up by the oolitic ac- 
Snail 
