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surfaces at least, much flatter, and in possessing less of the nodular or 
mamillary form. Their colour was also materially different; their ex- 
ternal surface being generally either of a light reddish brown, or of a 
greyish white ; on which circular or longitudinal patches, of a pur- 
plish hue, and possessing more transparency than the other parts, 
were irregularly disposed. On breaking these flints, the purplish hue 
and slight degree of transparency, were found, in many places, to 
pervade the whole substance, whilst in other places they did not enter 
far beyond the surface. The colour of the interior part of the flint 
also varied considerably in different specimens, being in some chiefly 
of a greyish white, and in others of a brown colour, in which a red- 
dish or purplish tinge was discoverable : the more transparent purple 
patches, already mentioned, were seldom of so dark a hue in their in- 
ternal, as in their external part. 
Slight traces of organization might be discovered with the naked 
eye, in many parts of these flints, but particularly in the more trans- 
parent purplish patches. These were also thus seen to be surrounded 
with a grey opaque matter, which Mr. Townsend considered as the 
fleshy or cartilaginous coat, analogous with that which is known to 
invest the interior harder part, in many coral bodies. On these flints 
being immersed in water, Mr. Townsend discovered that they were, in a 
great measure, hydrophanous, and that the traces of organization were 
thereby rendered much more beautiful and distinct. 
Returning, in the autumn of 1807, from a visit to Mr. Townsend, 
then residing at Bath, I was agreeably surprised to find, that on the 
road between Henley and Wycombe, and on Wycombe Heath, this 
kind of flint existed very plenteously, the roads being here repaired 
with such of them as were ploughed up in the adjoining meadows, 
or dug out of the neighbouring pits. Proceeding westward along the 
cross road through Amersham, Cheyness, and Chorley Wood, in 
Buckinghamshire, to Rickmansworth, a tract of twenty-seven miles, 
VOL. II. s ’ 
