447 
Fig. 28, of the same Plate, is a small silicious boulder, being rounded 
by attrition, of a fragment of silicious wood. It was found in the 
gravel-pits at Hackney. 
Fio' 15, and 17, in Plate VI. represent two specimens of a sub- 
stance which is sometimes found in the chalk-pits at Cherry Hinton, 
in Cambridgeshire. They have been supposed to approach very 
near in resemblance to the juli of the larch-tree ; from which they 
differ, how^ever, so much in some respects, as to ha\e induced 
Dr. Parsons to have considered them, rather as the roots of a 
plant, than the parts of fructification. The appearance which they 
exhibit does, however, certainly support the opinion of their having 
been either aments, or cones, of some tree not now known, at least, 
to the European botanist ; whilst, on the other hand, the situa,tion 
in which they are found, yields matter for ingenious speculation; 
since, instead of being found associated with other fossil vege- 
tables, or in matrices which have originated in the decomposition 
of vegetable matter, they have, I believe, only been found m chalk, 
which has proceeded chiefly from aqueous deposition, and in part 
from the decomposition of animal, bnt certainly not of vegetable. 
The other fossil remains of fruits on this Plate are all from that 
fruitful mine of fossils, the Isle of Sheppey : and, in common with 
most of the fossils obtained from this part, have so much pyrites 
enter into their composition, as renders their stay in the cabinet o t e 
collector, in general, but very short, from their proneness to decom- 
pose after having been exposed to the air. This has been the case 
with the specimen represented at Fig. 5 and 7? which had evident y 
been the stone of some drupaceous fruit, and which was so com 
pletely pyritous, that, on being cut, the polished section, repre 
sented Fig. 7? shone with the most brilliant golden lustre , t e 
traces of its texture not being discoverable without the aid ot a 
