54 Dr. Wallich on the Identity of the Chalk 
One of the conclusions I draw from the data afforded, is that 
the period at which perfect consolidation of a given stratum 
of flint takes place (leaving out of consideration at present the 
fissure-flint, which involves widely different issues, of which 
I may have something to say on a future occasion) is con- 
temporaneous with the consolidation of the stratum of chalk 
underlying it; whereas the period of ultimate consolidation 
of the contents of the closed cavities would appear to be inde- 
finite. Some have apparently become consolidated at the 
same time as the enclosing flint nodule. ‘This would seem to 
have occurred in those cases in which there is no trace of 
cavity left—the materials, entrapped as almost solid lumps of 
mud, with no more water than was just sufficient to keep them 
in a stiff paste, having filled up the entire space and become 
finally merged as a solid core in the substance of the sur- 
rounding wall of flint. In other cases the materials would 
appear to have become consolidated after an indefinitely length- 
ened term, leaving central cavities devoid of fluid, and bounded 
either by a glistening mass of minute quartz crystals or of 
delicately mamillated chalcedony with an intervening layer 
of reddish or greenish jasper between the crystalline layer and 
the substance of the flint. Where water is present in a resi- 
duary cavity, so is some remnant of unconsolidated material. 
Of course, in the whole of the examples of which I have 
spoken in this paper, I have purposely left out of sight such 
nodules as have formed around a distinct portion of sponge- 
structure. They havea perfectly distinct history of their own. 
I would here allude to an additional proof I have to offer 
of the contents of the hermetically closed cavities being in 
the strictest sense “¢nclustons,” as distinguished from any 
solid material that may have formed part of the nascent 
flint mass itself. It consists in the important fact that, but 
for the superior cohesiveness (the “ ¢dio-attraction”’ of Mr. 
Graham) of the nascent nodular masses, and their stubborn 
refusal to mix with water, in no instance in which free water 
had been admitted along with solid material in any consider- 
able quantity, as compared with the internal area of the cavi- 
ties, would the finally consolidated mass be found (as it con- 
stantly is found, whether in a finely or coarsely granular state, 
or a compact and solid cherty mass) resting quite loosely 
within the cavity like the kernel of a hazelnut within its shell, 
Under no other possible or even conceivable condition than 
those resulting trom the hermetical closure of the cavities 
from the beginning, would the imprisoned water have remained 
to this day unexhausted, even assuming what I believe to be 
impossible—that the said water, instead of having been directly 
