THE JURASSIC DEPOSITS WHICH UNDERLIE LONDON. Too 
strata of those ages in the West of England and in Normandy thin 
away and disappear as they are traced towards the east. 
(3) But about the commencement of the Great-Oolite period the 
ereat ridge of Paleeozoic rocks occupying what is now the south-east 
of England and the north of France began to be submerged, and 
the strata now for'the first time described were then deposited. 
What was the original thickness of these Great-Oolite strata in the 
metropolitan area, we have no means of knowing, as these deposits 
appear everywhere to have had their upper beds removed during the 
great Neocomian denudation. 
(4) The Great-Oolite strata which were thus deposited on the 
southern flanks of the great Paleozoic axis probably, however, 
never extended over the northern half of that axis. This is shown 
by the evidence of littoral, and even of estuarine and terrestrial 
conditions, in the Great-Oolite strata found at Meux’s Brewery. 
At this period there appears to have been an extensive tract of dry 
land lying to the north of the Great-Oolite sea which covered what 
is now the south-east of England and the north-east of France. From 
this land were borne pebbles of various hard rocks, of coal-measure 
sandstone, and of coal, which we now find in the bands lying at 
the base and the summit of the series of Great-Oolite strata at 
Richmond. 
(5) That the submergence of the Paleozoic ridge, which took 
place during the Great-Oolite epoch, was continued during the 
period of the Middle Oolites, we have sufficient evidence, as already 
pointed out by Mr. Godwin-Austen. The “ Lower Greensand” 
beds of the North Downs, between Sevenoaks and Farnham, often 
contain fragments of considerable size, and sometimes become almost 
conglomeratic in character. ‘The pebbles in these beds consist for 
the most part of quartzite and other hard rocks, evidently derived 
_ from the rocks of the great Paleozoic axis. But, mingled with 
these, we find a considerable number of fragmentary, waterworn, 
and evidently ‘derived ” fossils of unmistakable Jurassic affinities. 
From an examination of great numbers of these derived fossils, I agree 
with Mr. Godwin-Austen and Mr. Meyer in considering that they 
represent both the Lower and the Middle Oolite. But I am at the 
same time convinced that the fossils of Middle-Oolite age occur in 
such situations in much greater proportions than those of the Lower 
Oolite. Taking these facts in connexion with that of the presence 
of Middle Oolites under the Weald, as revealed in the boring at 
Battle, and the evidence of the general deepening of the Jurassic 
sea after the close of the Lower Oolites in the Anglo-Parisian basin, 
we are led to the conclusion that the Middle-Oolite strata originally 
overlapped those of Great-Oolite age, and probably extended right 
across the Paleozoic ridge. Thus we should conclude that during 
the period of the Middle Oolite the great Paleozoic axis was com- 
pletely submerged, and that the deep-water Oxfordian Clays of the 
north of France and of central England were deposited in a con- 
tinuous sea wherein the rocks of the Paleozoic ridge formed at most 
only a shoal. 
i Sa Ni 
