MR. F. D. LONQE ON THE FORMATION OF FLINTS IN CHALK. 155 
surface of growing Hint, where the consolidation of the granular 
material is not so complete as in the interior. 
(3) Another and more exceptional class are the huge pot stones 
or “ paramoudras,” as they have been called. 
These masses are apparently formed of pure black flint, like that 
of the smaller nodules, and to have been formed by the same 
concretionary action. 
They generally have tubular hollows, which, when undisturbed 
in the chalk, are filled up with chalk, or silicio-cretaceous material 
like the coating of the smaller nodules. 
These columnar masses would seem to be merely large concretions 
formed in sinks or perpendicular lines of drainage, made by water 
gravitating down, but only partially hollowing out the chalk. These 
pipes furnish larger cavities for the accumulation of water, than 
those in the more compact chalk around them. The larger quantity 
of water percolating through these sinks has caused a larger 
accumulation of silica, and the growth of larger concretions. 
The dimension and forms assumed by the various flint nodules 
would seem to bo due to the quantity of silica brought within 
reach of the concretionary action. Each nodule appropriates the 
silica with which it is environed, and when that is absorbed the 
further growth of the nodule ceases. 
This would seem to explain the different sizes, as well as the 
different forms of flint, and would also account for the scarcity of 
very small nodules now to be formed. Assuming that flints were 
formed since the consolidation of the chalk, the conditions requisite 
for their growth may have long since ceased to prevail. Even the 
“ baby flint ” was not born yesterday. 
