pebble of like kind, is charged with yellow-Tpots of a light-oehre
colour, from the fixth of an inch , diameter; and’under.
N°. iii. A very-blue violet: purple ground'^ granules lighter coloured,.
thinly difperfed from’ the eighth of: an inch and under in
diameter,-' a .beautiful ftone fromithe beach' in Mount’s-Bay.
N°. iv. We have alfo. the porphyrites . with larger grains, and a
green ground, which ftone though-not of a purple colour, yet, being
of like confiftence and texture,, muft be ranged alfo among the
porphyrites. " p
N'. v.. Dr. Woodward. takes notice o f .“ a ftone " finely varie-
« gated with fpots -of’ red. and-:white; with flakes of white talc in
“ it, found near Calftock, in .Cornwall, called with us the Worm-
“ Seed Stone, becaufe thick :fet\with fmall bodies-not unlike the
« Semen Santonici,. or Worm-Seed; fomewhat- related (fays he) to
u the porphyry kind.”
I have. yet found, thefe - porphyries .only in nodules'; -but fo many
being to be-feen, elpedally after .a ftorm,onrthé' fea-ftfore o f Mounts
Bay, particularly near it is mot unlikely
that there may be fane veins óvflratfc of them in-the fimk
rocks under the fea, though I have, : upon my' fear che's' among die
rocks-at low-water, notdifcowäed any;. The'ptÄphy^iwM^Wöi^lfc
formerly peculiar to Egypt,f and much a d m i r e d its’ieölöür'äöd#
hardnefs. The ancients had a method- of '#Oïking' it ydthhtöOlsp
but that method is aa yet'unknown to thé fiiódëtafei 'Tt>ls'#foïöfew^
grained kind of granite,; with its charge Or fpótS fcnorettfeatly placed,
and more diftinétly finifhed. fe
s e c t . v. It has been generally held, that d n CofhWalb'wë''hafe no'ftälac-
Offtakaites tites, but this is a miftake; for fome fmall drop-ftones or ftaläftites
in ComwaiT have been font to the Royal Society ■ from7 Peridinas: ca ftlé ,laid to
have had a ftrong fc en t'; and in the caves* oft a7 dliff, neä'r' the
Holy-well, in the parifh o f St. Cuthbert,;there are feveral; ftillati-
tious productions of a fparry kind. Some are 'gritty,' and their grit
little harder than-chalk; others are more ftöny, and hang from the
roof in fangs,• like the anemone root,- but fometimes in fmall tubular
ftaladtites with green and fometimes- red' cffioreicenciesi' The
fame fparry juice forms large bunches of ftötié’ bn the Tides ..of ;the
caves, and as i t drains through the fand, and ’ blown' fragments “of
fhells, fixes both, forming itfelf into--thin prominent wkvy ’edges,
with quadrangular cavities between, ■ making a pretty kind of fretwork.
On the floor of thefe caves: the feme'ftbfly -juicë'‘forms a
more uniform mals, Ipreading itfelf into a fluor of the alabafter
‘ Cat. vol. I, page 64, d.36. . * Grew’s Muf. R/Si page 320. •'
kind
kind; The fifata o f this incruftdtaon arenas many as the fucceffiye
indurations, eafily diftinguilhed, the under-part of each!ft'rmitm being
BfOWner and' rtlore^earthyjftehe upper-part more white and pure, • the
more impure parts of the liquid fettling neareft the bottom. The
famples I have from thefe caves, ^afe ’from half inch to fix inches
thick, icoating tlfe-pfafaberances', well, |J|1 the depreflfons o f the
rocks' theyTall mpofi,' qfually 'at- dtfj^hicknefs; but--where the rock
and the e^ e i' ©ft thajtcqn-
oavit|> upon ^l^^^he'alabafter isdthicker, better cloude% and of
I ^ 0 ^ gfiirf^an'drs’;Cbafeqt]entlyi)fitter for!* pbliftiiqW and maklhg
lafger WafesL' #he’ ;iyppb^paft# of - th'^ 'incraftation is covered ^bver
with a kind ofipurpk ppwder, ai-fort- b f mineral^eflWeffcence 4,
jtdtferious, ferm&Mfig ftroiiglj#%ith acids;'; Jndthe' microfcope k ap-
pears^oolly, and dike thfebhoots o f da'dip tbtriolicfobftances-;- 'but that
the'filaments which' fhdofftqtn vitriol- dre '\#dte,; and the thrMds p f
this; fefe life tranlparefit purple cfeiihg aiacfi other in aiLdife6fion&: '^
learned ’Mr. Rfiy^mentionv the ,ym’foiflggftone\,fliggedo>im sect. vi.
Cornwall, which, being once well heated at the fire, retains its warming-
warmth a great while. Dr. Plot (Oxfordfliirc, page 258) -fays this ft™e‘
ftone 'wilffoontinue warfn/eight o f ' ;ten- hours', and gives^felieft-ia
feveral pains, ■ particularly in thofe of the internal hemorrhoids; and
pa^efl2^3,v trails itj
dufijf. & folidifyriim- ctpiid Corritibienfes Warming-ftone. In ;York-
£hire^hey have a ftone of' this property; • confifting of dark^gtey
glofly talk with fome white Ipar interpofed betwixt the flakes of it,
which, Dr. Woodward (Cat. vol. I. page 62^0 d | 7 f .)SlaylfPthe
people lay in 'their beds ini cold, weather at their feet, becaufe, when ,
once heated, it retains the heat- a great while s.
In a- copper-mine, called Nancbthan, -near- Redruth, they have s.wimming-
a ftone' which they call the Swimming-ftone.. It confifts ofTeiftili- *0"*1'
near lamin&.as thin as.paper, interfebting each other iii all- directions,
and leaving unequal' cavities of yaribus angles between the -fepid.
The ftrudture is therefore very cellular, an#-makes the ftone fo
light, that it Iwims oh water. It is of a yellow'goflan' colour, and
as to its exteriour, has fome refemblance to a light kind of, cavernous
lapis calammaris, which I have had' from Wirkfivorth, near
Derby. I have not heard of this ftone’s being found any where in
Cornwall but in this work. ';S.
d SuMcifed“ to be the flowprs of -cobalt. IB
0 I have obferved flie fame pjiTple efflorefeejifo
cies on a damp \{tuckbed wall in the chapel at
St.ichatel^aM|tjrHt..p. . •
f In which quality however it is inferiour to the
Spanilh Ruggiolal (mentioned in Willughby’s
Travels through Spain, page 471)* which are
broad plates, like tiles, bvit out of ,a' mountin' of
■ fed'fait heat; Cardona^- %hich, being; wett hieated
on both' ndes, vdli^keep warm .tw^ity-four hiotit^.
? Hill,; ^age 553,- .calls this ftone The blueifh
white brittle T'elaugiunl.
o f