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Many geologists have endeavoured to trace the origin of white 
chalk. Mr. Lyell has remarked, that chalk which appears-to an ordi- 
nary observer quite destitute of organic remains, is nevertheless, 
when seen under the microscope, full of fragments of corals and 
sponges, the shells of foraminifera, and still more minute infusoria. 
The bold idea, that chalk was of animal origin, produced by the de- 
composition of testacea and corals, was considered by some naturalists 
quite vague and visionary, until its probability was strengthened by 
new evidence, brought to light by modern geologists. Lieut. Nelson 
and Mr. C. Darwin have published some valuable observations in 
support of this argument; but the followimg are the most remarkable 
facts relating to the Chalk formation which have ever appeared. 
In the Transactions of the Royal Academy of Berlin for 1840, 
Prof. Ehrenberg read a most important and highly interesting paper 
on the numerous animals of the Chalk formation which are still to be 
found in a living state. He enumerates fourteen forms which have 
been noticed by different authors, —six Echinoidea, six Mollusca, one 
Coralline and one Polythalamia, and adds fifty-seven new species ; of 
these, nine are calcareous-shelled Polythalamia, and forty-seven sili- 
ceous-shelled Infusoria; of these, thirty belong to the undoubted 
chalk and Sicilian marls ; the remaining twenty-seven occur in marls 
which contain so many well-known animals of the chalk period, as to 
leave little doubt of their contemporaneous origin. Several of these 
siliceous Infusoria have been observed im England, such as Mragilaria 
rhabdosoma and F’ striolata in white chalk from the Gravesend quar- 
ries ; and in flint, several species of Xanthidia and other genera have 
been noticed from Kent and Sussex. 
“Mr. Lonsdale, on examining, in October 1835, in the museum of 
the Geological Society of London, portions of white chalk from differ- 
ent parts of England, found, on carefully pulverizing them in water, 
that what appear to the eye simply as white grains, were, in fact, well- 
