XXIV 
THE VOYAGE OF H.M.S. CHALLENGER. 
Sponge spicules ami Radiolarians being also present, while the calcareous tests of Fora- 
minifera were absent. These deposits of microscopic organisms, in their richness, extent, 
and high latitude, resemble the siliceous deposits of the Antarctic already noticed by 
Hooker. Bailey’s researches proved that localised deposits were formed in the high seas, 
in which not calcareous, but siliceous, remains predominated. The excellent state of 
preservation of these siliceous organisms, and the fact that many of them still retained 
the soft jiarts, led him to conclude that they must have been living up to a very recent 
jK*rio«.l, not necessarily at the great depths where they were found, but probably drifted 
from shallower deposits. 
About the same time Bailey published his work on the origin of greensand and 
its fonnation on the bottom of modern seas.^ Ehrenberg had long before observed a 
pseudomorphism of the calcareous shells of Foraminifera in the Chalk into silica. As 
early as 1845 Bailey had called attention to the casts of Foraminifera in the Eocene marls 
of Fort Washington.'^ ]\Iantell stated in 184G® that casts of Foraminifera and their soft 
parts were preserved in flint and limestone, and that the chambers of the Foraminifera 
were often filled with calcite, silica, or silicate of lime. But Ehrenberg was the first to 
show the connection between greensand and the Foraminifera, and to throw light on a 
point which had long puzzled geologists. In 1855 he says that, in all the examples be 
had examined up to that time, greensand must be considered as due to the filling up of 
organic cells of Foraminifera, like a lithoid mould.^ Bailey verified Ehrenberg’s results 
from the examination of a number of Cretaceous and Tertiary rocks of North America. 
Pourtalds in 1853 announced that he had obtained from a depth of 150 fathoms, in 
lat. 31' N., long. 79'’ W., a dei)Osit formed of almost equal parts of GlohigeHnae and 
black sand, probably greensand.'^ Bache showed these and similar samples, taken in the 
region of the Gulf Stream, to Bailey, who found in them casts of organisms, some of 
which were “well-defined greensand, others reddish, brownish, or almost white.”® He 
concludes that these glauconitic cjists have not been transported from ancient formations, 
but have Ijeen formed where they were found in the same manner as in geological forma- 
tions. He states that his own and Ehrenberg’s researches prove that other organisms, 
Ijcsides Foniminifeni, may serve as moulds for the greensand, and he notices that with 
the well-<lcfined casts are a.ssociated green grains less regular in form, “having merely a 
rounded, cracked, lobed, or even eoprolitic appearance.”^ The phenomena accompanying 
the decomposition of organic, substances, he says, are closely connected with the formation 
of this mineral — a green or red silicate of iron or almost pure silica. 
In 185G I>ieut. Berryman, in the steamer “ Arctic,” sounded across the North Atlantic, 
and obtained samples of the deposit from thirty-four points between St. John’s, New- 
• /'rnc, Jlndnm Soc, Sal. llut., vol. V. pp. 3fi4 36S, 1856. * Amer. Journ. Sci., vol. xlviii. p. 341. 
’ /'Alt Tmtu., p. 466, 1S46. < MonaUb. d. k. Akad. Berlin, 185.5, p. 172. 
I^|x»rt U.H. C'oswt Surrey for 18.'i3, Ajip., p. 83. ® Loc. cit., p. 367. ^ Loc. cit., p. 3C8. 
