22 
Mr. William Phillips on the 
In some instances these naturally fractured surfaces, while yet 
imbedded in the chalk, were so close together as scarcely to admit 
the edge of a knife between them; ift others they were half an inch 
apart, the intermediate space being filled with chalk. As the opake 
white substance, which in some cases only surrounded the edges of 
the fractured surface, did not project beyond the central part, still 
retaining the black colour of the internal part of the flint, it is clear 
that it was not a coating; but on the contrary, this circumstance 
seems to furnish strong, if not conclusive evidence of its being the 
consequence of disintegration, proceeding from causes that have 
not hitherto been explained. The alluvium of the surrounding 
country corroborates the supposition; every where it includes a 
multitude of fragments of flint, the broken surfaces of which always 
exhibit the same appearance of disintegration. 
It is also I believe to the progress of disintegration that we are 
to ascribe the existence of the white opake coating by which 
the mass of every flinty stratum is more or less covered, while yet. 
in its natural bed. In no instance did I observe any well defined 
line of separation between the flint and the opake coating, which 
not unfrequently is half an inch thick, and which by exposure to 
the sea becomes more compact, and hard enough to admit of a 
conchoidal fracture. Between its outer surface and the black flint, 
it is not uncommon to observe two or three thin bands of flint. 
If the white substance be the consequence of disintegration, it 
seems remarkable that these bands should have been thus left 
untouched. In order to ascertain the nature of the white substance 
surrounding the flint, I selected with care three portions. One 
from without the band— another from between the band and the 
flint — and the third of one in w T hich there was no band. These 
my brother took with a view to determine what proportion of each 
