82 Dr. G. A. Mantell on the Animalculites of the 
full action, with its floods of melted rocks, its opened fissures, 
and its fountains of boilmg waters and jets of heated vapours ?” 
For a full explanation of these views I refer to the original paper 
of Mr. Dana in the ‘ American Journal of Science’ for January 
1845. The elaborate work of Dr. Blum on the Pseudomorphous 
Minerals may also be studied with advantage*. 
I return from this digression to the consideration of the minute 
fossils which are of most frequent occurrence in our flints. The 
polythalamian forms are chiefly referable to the genera Rotalia, Ro- 
talina and Textilaria ; there are also some kinds of the compound 
foraminifera, but these are comparatively rare, and I have not yet 
examined them with sufficient attention. In some slices of flint 
prepared by Mr. Darker from the Paramoudra of Ireland, polytha- 
lamia are very numerous. The shells or cases invariably appear to 
be silicified, and the cells of the dead shells to be filled with flint. 
By dead shells I mean those in which the animal was dead, and its 
soft parts removed and the shell empty, before its immersion in the 
silex ; for I can now bring unequivocal evidence to prove, that in 
many examples the animal itself must have occupied its shell, and 
all its soft parts been entire, at the moment when it became en- 
veloped by the siliceous fluid. A specimen figured in the ‘ Me- 
dals of Creation ’ first directed my attention to this interesting 
fact ; and several specimens both of Rotalie and Textilarie have 
since been discovered, which confirm the opinion I then ventured 
to suggest. 
In illustration of this highly interesting fact, I select on the 
present occasion an atom of flint (scarcely larger than a pin’s 
head) discovered by Mr. Lee, in which are imbedded two Rotale, 
having the cells filled with a rich amber-coloured substance, that 
under a high power presents a granular structure analogous to 
that of the body of the recent Rotate. In these fossils the soft 
parts appear to be in the state of molluskite, or they may have 
undergone silicification ; the mineral being coloured by the ani- 
mal matter. To persons unaccustomed to the microscopical ex- 
ploration of objects of this nature, these specimens may seem to 
be merely casts of the interior of the shell; but to the eye well- 
instructed in the character of such remains, they will at once be 
seen to be entirely dissimilar. I would content myself with re- 
ferring to the ‘ Medals of Creation,’ in proof of the above infer- 
ences, did I not know that many of the Fellows of this learned 
* The experiments of Mr. Jeffrys, published in the Report of the British 
Association for 1840, confirm these opinions, and prove that simply by the 
agency of heated water and vapour, silex will be dissolved, and be precipi- 
tated upon the cooling of the liquid or vapour. In one of these experiments 
several pounds of silica were deposited on substances placed within reach of 
the current of vapour. 
