xo6 N A T U R A L H I S T O R Y
of flbian marble of the ancients j although any black, hard marble
will indeed anfwer the purpofes of abouch-ftone.
• N 9. 7. Jalpers are to be found among our pebbles, more elpeci-
ally of the black and yéllövv kind , • but of the green jafper I have
yet feen none found in this county, p
sect, nu It has been generally held by Naturalifts that we have no* flint®
Pats. nfethfe in Oorhwall, but this % a miflxke. w Betwixt the towhf o|S
Penzance' and Marazion there is a beach of pebbles two miles and
three quarters long, among; which many hundred flints may be
picked up every day 5 and left it fhould be infinuated that - thefe
flints may poffibly be foreign, and; brought in ballaft by fhips, I
muft obferve, that in the low-lands of the pariffi of Ludgvan, fcarce
a muiket-fhot from the faid beach,ifr-a^pWiettic^ed • A c Vorlas,
there is a Jlratum of clay about three feet under the grafr: the'. clay'
is about four feet “deep. In this clay,' immerfedfrom one to foui
feet deep, (fometdmes deeper) flints are-difcovered in greatiuumbers,
their ik e from the bignefs of a man’s fift to that'of a • bedfc, their
coat nearly of the colou* o f the clay, (as in: chalk, we find’ their «X»
teriour infe&ed with the chalk-bed in which they lie).' and their
inward part died with the feme colour more than half way;ȕthe
other pat, near the middle, a common, corneous, brown flint. In
the feme , bed o f ‘clay, I find fea-pebbles of opake white quartz;
and fome ihingle; fufficient and evident' veftiges of the univerfel
deluge.,»!! find dfo many finall blué W«ithi'aJi Aefr
angles o n ; an equal evidence, that as the advancïng'wateïs Of'.the
deluge introduced the productions of; the :fea, fo the departing waters
of the feme cataftrophe frequently depofited ftones and ffag4
ments tif ftones from the hills: both llréw,'that the
as it was teftffiy the flood, andafe confequently teftimonies that the
flints found in it muft be native, and the growth of Cornwall.
Thé flints o f this bed of clay are brown within, but on the beach
we have a remarkable variety, and One now before me' of an opake
white, is of as fine texture, and as high a poliih, as any Carnelion
I have ever feen.
sECT.m. Pebbles found on the fea-fhore are generally of the fame flattifh
shape and^ oval fhape. This ihape is therefore attributed (and for the moft-
pebbies, and part not unjuftly) to the agitation of the fea, which, by continually
raquiSunto ro^™g fkm to and fro, againft the rocks and againft one another,
wears off the angles, and neceflarily reduces them to their globular
figure: but what exercifes the attention of the curious, is, that
pebbles are oftentimes found in clay and gravel-pits many miles
from the fea, and yet of the feme orbicular ihape as thofe on the
fea-
O F - € Q R N W A X L. IOy
fea-ihore; nay, fome ipfolfe/sfe . inland pebbly g are fometimes large
from ten to twenty pches, and fome three and fours feet diameter.
The ijueftion th®;efore is, Whepce. this fimilarity ,o£i ffiape ? How
come the. inlaud pebb&s to be|of;that ,ihape, which,/ ip foch numerous
inftances as the fea-fliore;s|nd riyers affprd us, -is. majjjfeftly
owing only to the agitation of fea and river-watefcs. Dr. Woodward
^(-who left few. parts of Natural Hiftory unattempted, and
many particular*very fuccefsfulLycexplained) labours, hard to prove,
that the inland «pebbles are indebted to the departing waters of the
Deluge for their* roundnefs ; and that thefe .waters had'the feme effect
upon them as the fea upon thofej;f)f j tfie fhores.: ,but it is very
Juftly replied to.-this opinion, that ffie, departing waters of the deluge
-had neither time ikm:< fufficient force in general, aor.yfofence ,qf
agitation enough in all fituations to produce’the .eifedb in qyeftion;
the caufe therefore affigned is not/, equal ta^the»; effect,- j and all the
phenomena in pebbles produced Jby him", ;ipay be, rationallyxaccounted
for upon much lefs diiputable principles *. The truth" is,
this' pebbly form is either natural or adventitious; where the form
is adventitious, »it is owing either to-the force. or river-waters;
on the fea and river-beach thofe pebbles of the fofter kinds, and
thofe which: f appear to have been fragments .of die adjoining rocks
(or nodules which/ never arrive to the fize o f rdefes) owe their
||©unanefsffia the neighbouring "waves ; a t. the feme time it muft
be»confeifed, that many which are on the Chore, as well as moft of
the-inland pebbles, are really found in their own original, and natural
forms in which they firft concreted. Natural pebbles may be fefely
diftinguifhed from faftitious ; firftj by their having a coat , or ihell
moftly- of an even thickneis, but of a different colour from the
inward fobftance o f the ftone 5 fecondly, when the pebble has a
nucleus* in or near (fee center, round which the body o f the pebble
is formed in fir at a ; thirdly» when the "fibres o f the body ipring
like rays from a .central point ; fourthly, thofe; pebhles, which have
nodulous buncheS'Or excrefcencies of equal hardneis to the reft o f
the body, may be looked upon as/iri the feme ftate and. figure which
nature left them in; fifthly, if u pebble ferments with acids, it is
not a natural one (Hill, page 406); but whether this criterion be
conclufive may he queftioned j for I cannot fee why ftones o f a
iparry bafe may not be formed into a pebbly figure by the - feme
" Ibidem ut fupra (if pnffim.
w The. ftone which Ur. Woodward (ibidem ut
fitpra, page 4.7,) lays fo much ftrefs upon, may
oe explained without having,recourfe to the de-»
farting waters of the deluge. 'This ftone conflftsr
of feveral fmall pebbles cemented together into
one 'nodule. more need be (kid, than that
the ground and the charge might be liquefeent at the
fame time; and though by; the attraction of fimi-
Iar parts the little pebbles were kept together in
feparate mafles, and the cement; at .the fame time
that it furrounded them, repelled them to their
own liriiits, yet belng both fupple enough to conform
to the force of external bodies, they became
compreffed and rounded,. and formed one nodule
under onp convex furface.
principle