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550 THE CRETACEOUS ROCKS OF BRITAIN. 
coast; off Tristan d'Acunha, at depths of 550, 1,000, and 1,100 
fathoms; and in the Molucca passage as above stated. Mr. 
Stallibrass has recorded the existence of strong currents between 
the Canary Islands at a depth of 1,000 fathoms.* 
Returning to the current phenomena of the Middle Chalk, 
the existence of surface currents is indicated by the occasional 
occurrence of drift wood, and of transported stones and blocks 
of rock, and, so far, these have occurred chiefly in the south¬ 
eastern counties. The layers of grey marl and marly clay again, 
which occur as thin seams between the thick beds of pure chalk, 
are additional evidences. I think both these phenomena may 
be attributed to seasons of heavy rainfall, producing periodic 
land floods, whereby an unusual quantity of fine muddy detritus 
and soil was poured into the sea from off the neighbouring lands, 
and was carried to great distances by the surface currents. 
There is another peculiarity of the Middle Chalk which may 
possibly have a direct relation to currents, either at the surface 
or along the bottom. This is the abundance of fish remains, 
and here, again, we find such remains especially frequent in the 
south-eastern counties. Dr. Hume was, I believe, the first to 
suggest a connection between currents and fish remains. Writing 
of the Lewes and Brighton district, he remarks, “ a further point 
to note is the abundant fish fauna of this district. Whv is this ? 
The answer, perhaps, is not far to seek. The current will evi¬ 
dently carry along with it large amounts of [food] material derived 
from the littoral area, and far more suitable to a piscine palate 
than the usual minute pelagic fauna of an oceanic region. 
The result would be that comparatively shallow water Teleostean 
fishes, such as Beryx, would have their range greatly extended 
seawards, while the rich increase in food material would tend 
to bring together large numbers of predatory fishes, especially 
sharks such as Lamna.” 
Bathymetrical Conditions. 
Coming now to the consideration of the depth of water below 
which our Middle Chalk may have been accumulated, we must 
bear in mind the inferences already indicated under the head of 
geographical conditions, and must remember that there were 
tracts of land both to the west and the east, as well as to the 
south, of the Anglo-Gallic sea. Consequently, this sea was not 
an open ocean, and no part of the Middle Chalk is likely to have 
been deposited in very deep water nor very far from land. By 
* Journ. Soc. Tel. Eng., 1887, 
