9 
overpowered by the immensely greater amount of calcareous 
sediment, which arises from the aggregation of the skeletons of 
dead Foraminifera. The similarity of the deposit, thus composed 
of a large quantity of carbonate of lime and a small percentage of 
silex, to chalk, which was first pointed out by Ehrenberg, is now 
admitted on all hands; nor can it be reasonably doubted that 
ordinary metamorphic agencies are competent to convert the 
‘‘modern chalk” into hard limestone, or even into crystalline 
marble. * 
Although the Globiyerina ooze is the most widely-spread 
material of the sea-bottom in the intermediate zone of the Atlantic 
and Pacific oceans, other deposits of green sand, dredged up by 
Count Pourtales off the coast of Florida, when examined by 
Professor Bailey were found to be casts of Foraminifera, consisting 
of a mineral resembling Glauconite. Messrs. Parker and Jones 
discovered similar casts in process of formation in specimens of the 
sea-bottom of the Australian seas, and during the cruise of the 
‘* Challenger” a similar deposit has been observed in the course of 
the Agulhas current near the Cape of Good Hope. As bearing 
upon this, Ehrenberg had discovered that many of the green grains 
of the green sand of Lower Silurian age of Russia consist of 
silicious casts of Foraminifera. + 
Further, the recent observations of the ‘‘ Challenger’’ have 
shewn the interesting fact that in the midst of the intermediate 
zone, at depths of 3,000 fathoms and more, the sea-bottom no 
longer consists of Globigerina ooze, but of an excessively fine 
red clay.{ Professor Wyville Thompson states that the first four 
stations in the first section between Teneriffe and St. Thomas, at 
depths from 1,525 to 2,220 fathoms, show Globigerina ooze. 
From the last of these, which is about 300 miles from Teneriffe, 
the depth gradually increases to 2,740 fathoms at 500 miles, and to 
2,950 fathoms at 750 miles from Teneriffe. The bottom in these 
two soundings might have been called ‘‘ grey ooze,” for although 
its nature has altered entirely from the Globiyerina ooze, the red 
clay into which it is rapidly passing still contains a considerable 
admixture of carbonate of lime. The depth goes on increasing to 
a distance of 1,150 miles from Teneriffe, when it reaches 3,150 
fathoms ; there the clay is pure and smooth, and contains scarcely 
a trace of lime.§ This red clay has been traced for a distance of 
1,900 miles from east to west, and chiefly consists of silicate of 
the red oxide of iron and alumina. 
It may be interesting to enquire whether the red chalk of 
Lincoln and Yorkshire may have any relation to this red clay, and 
* Prof. Huxley, “Contemporary Review,” March, 1875, p. 646. 
+ Brit, Assoc. Report, 1854, Sections, p. 84. Proc. Berlin Acad., June, 1858, 
Murchison, Siluria, 1867, p. 356. 
+ Huxley, ibid., pp. 651, 652. 
§ Proc. Royal Soc., vol. xxiii., p. 44. 
