MH. K. I). LONGE ON THE FORMATION OK FLINTS IN CHALK. 153 
it is the force which produces spherical lamination round a centre 
which is evidently the most important factor at work. 
The process of the conversion of the loose granular silica, in the 
coating, into hard vitreous flint, would seem to imply the further 
action of the attracting and condensing force — which acting upon 
the granular silica whilst undergoing a slow solution in its moist 
matrix — draws it, molecule by molecule, into the solid mass 
within. 
The manner in which flint is found enveloping or partially 
enveloping substances, would seem to suggest that the silica passed 
through a gelatinous state in the process of its accretion. Silica 
can be reduced to a gelatinous state in the laboratory, but I have 
no authority for suggesting that it has passed through such a state 
in the formation of flints in chalk. 
In his account of the formation of flint, Professor Green makes 
no allusion to the silicious coating with which flints are covered, and 
I gather from Professor Sollas’ treatment of the subject that this 
theory of the flint being formed from the silicious coating is new 
to science, and that it has been hitherto attributed to the decay of 
flints rather than to its growth. 
In chalk pits, in the upper chalk, which comes to the surface in 
this part of Norfolk, flints abound in all shapes and sizes. 
The formation and growth of flint nodules appear to have taker, 
place after the consolidation of the chalk, and when it has been in 
much the same condition as we now see it ; and it seems probable 
that the process of concretionary growth would continue so long as 
the flint remains undisturbed in the moist chalk, and is supplied 
with the materials requisite for its growth. 
Flints are often found enveloping foreign substances, which are 
not uncommonly organic forms, such as sponges or shells silicified, 
and incorporated in the flint nodules, and which appear in some 
cases to have been the nucleus round which the flint nodules grew, 
and it has been thought that all flints have thus originated — as in 
the case of oolitic grains. 
These foreign bodies are, however, often found in flint in such 
a position as to point to their having been enveloped by the flint 
as it grew. The notion that flints are all silicified sponge or other 
organic forms has been abandoned. 
A not uncommon phenomenon is the presence of shells, echinidae, 
