THE GEOLOGY OF LONDON. 
3 
with turpentine, to let a drop of Canada balsam fall on it, 
warming it at the same time over a lamp. Being now covered 
with a piece of thin microscopic glass, we may soon ascertain 
(by the aid of the microscope) whether we have been successful 
in obtaining specimens.” * * * § 
The chalk is considered to have been formed in a deep and 
open sea, and indeed the researches which have been carried 
on in the North Atlantic Ocean show that materials for a con- 
tinuous bed of limestone, with flint nodules, is now being 
deposited there. Professor Huxley, who has described the ooze 
derived from depths between 1,700 and 2,400 fathoms, con- 
siders that 85 per cent, of the whole belong to one species of 
Globigerina (a genus of Foraminifera), 5 per cent, to other 
calcareous organisms of at most four or five species, and that 
the remaining 10 per cent, consist partly of granules of quartz, 
and partly of animal ( Polycystinece ) and vegetable ( Dia - 
tomacece) organisms provided with siliceous skeletons and 
envelopes.! These siliceous organisms give us the clue to the 
formation of the flints. They consist almost entirely of silex, 
which is generally aggregated round some nucleus of sponge, 
sea-urchin, or mollusc, and, as we now find them, they occur 
in nodules and bands. Their fantastic, shapes gave rise to the 
publication, a few years ago, of a humorous, though professedly 
scientific work, in which the author figured a number of 
curiously-formed flints which he had collected, and identified 
them according to the objects to which they had an apparent 
resemblance. Amongst these were a bird of paradise, some 
doves, hippopotami, sheep, and a pair of shoes ! These he 
brought forward as evidences of a universal deluge 4 
The Thanet beds, which overlie the chalk at London, but 
thin away northwards, § consist generally of pale-coloured 
quartzose sand, and were so named by Mr. Prestwich from their 
being best exhibited in the Isle of Thanet. Immediately 
beneath London they have a thickness of about twenty feet ; to 
the south Mr. Whitaker has noticed sections near Epsom, 
Cheam, and on the eastern side of the Croydon Valley. He 
remarks that the great pit east of Charlton railway-station 
shows a very long face of Thanet sand. The deposit is not 
very fossiliferous, but contains some remains of fish, mollusca, 
* W. Hislop, “ Proceedings of the Geologists’ Association,” vol. i. p. 388. 
f See u Manual of Geology,” by Jukes and Geikie. 
% 11 Facts and Fossils adduced to prove the Deluge of Noah.” By 
Major-Gen. Twemlow. 
§ Their occurrence at Sudbury, on the northern outcrop of the London 
Basin, where they had not previously been detected, has lately been made 
known by Mr. Whitaker. 
