1898] PROBABLE DEPTHS OF THE GAULT SEA 311 
It has already been pointed out that those authors who have 
expressed any opinion as to the depth of the Gault Sea have not 
given anything like the depths shown by these results based upon a 
systematic inquiry into the distribution of the foraminifera through- 
out the Gault at Folkestone (2). Previous authors, with the exception 
of Professors Parker and Jones, have based their results upon data 
afforded by a consideration of the groups of the mollusca, crustacea, 
and other of the larger organisms. These higher groups from 
modern deposits have, in many cases, only been specially dredged 
from moderately shallow depths. Although the bathymetrical range 
of these larger forms is in most cases rather limited to the shallower 
parts of the ocean, it appears to me extremely probable that current 
action, of which there is abundant proof throughout the Gault at 
Folkestone, has there operated in bringing together assemblages of 
testaceous remains from the higher continental slope on which they 
flourished, to greater depths where these accumulations took place. 
It is more reasonable to imagine the removal of the shallow forms 
to deeper areas than to suppose that the finer muds with foramini- 
fera-could be brought into shallower waters. 
The presence of phosphatic nodules, so abundant in the Gault, 
by no means indicates shallow water. That these are due to currents, 
and by the changes of temperature consequent on their inter- 
mingling, has been clearly shown by Murray and Renard (“ Deep Sea 
Deposits,” p. 397), who state that phosphatic concretions “may be 
found in all terrigenous deposits, and also along the edge of the 
abyssal zone in deposits of a pelagic type, which, however, from 
their nearness to land, still contain terrigenous elements.’ These 
authors also point out (p. 396) “that phosphatic nodules are 
apparently more abundant in the deposits along coasts where there 
are great and rapid changes of temperature, arising from the meeting 
of-cold and warm currents, as, for instance, off the Cape of Good 
Hope and off the eastern coast of North America. It seems highly 
probable that in these places large numbers of pelagic organisms are 
frequently killed by these changes of temperature, and may in some 
instances form a considerable layer of decomposing matter on the 
bottom of the ocean.” 
That current action played an important part during the deposi- 
tion of the Gault is, therefore, not only proved by the numerous 
lines of phosphatic concretions found at certain intervals, but also 
by the presence of green-sand seams and scattered glauconite grains 
found throughout the formations, 
The depths here given for each zone of the Gault are merely 
recorded for what they may be worth; for after all it is a result 
1 Professor Rupert Jones has already expressed to me his belief that the calculation 
made many years ago by him and his colleague Parker is probably of far less depth than 
it should be, 
