[Nov. I, 
P/ 'oceedings of Learned Societies 
5G6 
cuHar distinctive character. A few 
shells only, which may be placed among 
those which are supposed -to be lost, or 
among those which are the inhabitants 
of distant seas, are here discoverable ; 
the greater number appearing not to 
differ specihcally, as far as their altered 
state will allow of determining, from the 
recent shells of the neighbouring sea. 
In this bed, among the gravel and the 
shells, are frequently found fragments of 
foshil hone, which possess some striking 
’peculiarities. They are seldom more 
than half an inch in thickness, two inches 
in width, and twelve in length ; always 
liavirfg this flat form, and generally 
marked with small dents or depressions. 
Their colour, w'hich is brown, light or 
dark, and sometimes inclining to a green¬ 
ish tint, is evidently derived from an im¬ 
pregnation with iron. From this ira- 
nregn?<.tion they have also received a 
great increase of weight and solidity; 
from having been rolled they have ac¬ 
quired a considerable polish; and, on 
being struck by any hard body, they 
give a shrill ringing sound. These frag¬ 
ments, washed out of the stratum in 
%vliich they had been imbedded, are 
found on the beach at Walton, but oc¬ 
cur in much greater quantity at Har- 
tvich. 
Of the fiat rounded pieces described 
above, no conjecture can be formed as 
to the particular bone or particular 
animal to which they belonged. But, 
within these few years, an Essex gen¬ 
tleman found, on the beach at Harwich, 
a tooth which was supposed to have be- 
iong-ed to the mammoth. This fossil was 
kindly obtained, at my request, for the 
purpose of being exhibited to the mem¬ 
bers of the Geological Society, by my 
late friend Dr. Menish; and certainly it 
appeared to be part of a tooth of that 
animal. It had been broken and rounded 
by rolling, but its characters were still 
capable of being ascertaitied. It pos¬ 
sessed, in the softer parts, the colour and 
appearance of the Essex mineralised 
bones, so distinctly, as to leave not a 
doubt of its having been imbedded in 
this stratum; whilst in the enamel it 
manifested decided characters of the 
tooth of some species of the mammoth^ 
or mastodon of Cuviei*. 
The actual limit of this stratum lias 
not been ascertained ; it is however 
known to extend through Essex, Mid- 
dlese'i, part of Kent and Surrv, and 
tnroush lisrcfordslrire, Buckinghanislnre, 
s,:-d indeed much fu::her, both to the 
northward and westward. In many 
parts its continuity has been interrupted, 
apparently by partial abruptions of it, 
together even with a portion of the 
stratum on which it rests. The shells of 
this stratum have hitherto been disco¬ 
vered only in the parts already noticed. 
Blue Clay Steatum. 
This, the next subjacent bed, is formed 
of a ferruginous clay, exceeding two hun¬ 
dred feet in thickness. Its colour for a 
few feet in the upper part is a yellowish- 
brown, but through the whole of its re¬ 
maining depth is of a dark-bluish gray, 
verging on black. It is not only charac¬ 
terized by these circumstances, but by 
the numerous septuria which are dis¬ 
persed through it, and by the peculiar 
fossils which it contains. 
The dilference of colour observed be¬ 
tween its superior and inferior part, and 
which has generally been supposed to be 
ow’ing to a difference m the degree of 
oxidation of the iron present in it, ap¬ 
pears to be the result of a difference in 
the quantity of it, occasioned by the 
washing away of this metal in tlie upper 
part by the w'ater which percolates 
through it, and which runs off laterally 
by the numerous drains made near the 
surface. The dark-red colour of tiles 
made from the blue clay, tiie reddish-yel¬ 
low colour of the place bricks made of the 
yellowish-brown clay, and the bright- 
yellow hue of the zcashed malms, those 
bricks which are formed of the'yellow- 
clay which has been exposed to repeated 
washiho;s, are thus accounted for. 
The septaria lie horizontally, and are 
disposed at unequal distances from each 
other in seemingly, regular layers; and, 
as has been just observed of the stratum 
itself, they become of a paler colour, 
and it may be added suffer decomposi¬ 
tion, when placed so high in the stratum 
as to be exposed to the action of perco¬ 
lating water. They frequently include 
portions of wood piei’ced by the Tti'C- 
dines, Nautili, and other shells; and it is 
a fact that may be worthy of being at¬ 
tended to, whilst inquiring into their 
formation, that the septa of calcareous 
spar frequently intersect the substances 
enclosed in the septaria. 
^ This stratum is to be found not only 
wherever the preceding deposition ex¬ 
tends, bat in other parts also where that 
has been removed. The cliffs of this 
clay, at Shepey, extend about six miles 
in length; the more elevated parts, which 
are about ninety feet in height, being 
about four miles in length, and declining 
gradually 
