: 136ft^ N A f U R A l y f l I S 'Ï .Q / R Y
-'«n^informed °, yields notjbnjy arf?nic§k and fujphur, butba* j^wder
. t very near, if npt equal to, and^tjie,iamq as ultramarine. ,
1 ^ p tJ ie y e a t J 175,0^1 had ■ 'a Étnple pla(e)mupdic,
abundantly mixed with fpdtre; Tröhi.fe wort in Gwyriier’‘ pari;fh.
,1,11; may ^theref^ïei'he well-vyortfh^hile to en^tfe 'faMher- mm ...this
mundic,' whether ultramarine may be procurêd;frofn 'it in ally an-
fwerablè, quantity; ■‘and, fecondly, Whether-3it maybfdrVe^M plfr-
■ poles, orinerbafethe powers and quantity of fpeltre; and,.’ in con-
tinual fearching, other ufes, not now forefeen, may probably occur.
s e c t . XVI. Cryftals and mundics are frequently found, in the lame beds, and
relations by the inlpe&iön of feveral ipecimens, we may reft allured, that fome
famed st mundics were indurated before the cryftals, as’appears by the plain
times, Ihd ruupreffion made in the cryftals which adhered to them, and from
fon^ng which we may ealily feparate them; and other Ipecimens will as
T ' readily convince us that thl^ were indurated, fince the cryftals, being
formed into cappings and incruftations upon the cufpides of the
Cornilh cryftals, from which they have.'vifibly received the hexago-
n^l impreflion. Further: There is great realon to believe, that
mundics are perpetually forming (as is probably the cafe of all ores)
new combinations where they have proper room, liberty, Cnidus, and
fubjects to fix upon; for in~the fragment of a Cornilh cryftal
brought me, in the year 1752, from a mine which had layn idle
about. thirty years^I perceived an incruftatiori of granulated beiprink-
led mundic beginning to coat the cryftal in the fradure: now,
there is all realon to believe, that this cryftal was broke in the columnar
part when the mine was worked laft, which is betwixt thirty
and forty years ago, fo that this mundic incruftation muft ?have
fixed itfelf on this fraéfcure finèè jfiat term. '„The following &eidefct\
confirmed the fuppolition : ^Having laid by? feme mundics .•in.1 a
drawer, and coming about two years after id- examine them, I
fbund.feveral glebes of yellow-mundic, which were feparated.when
. I put them by, flicking clofe together; one glebe had picked up a
bit of blue vitriol, a grain of lead, a grain of copper, and a grain-
of cryftal; and the yellow-mundic had alfo Ihot round about, and
clofely embraced a piece of the plate-mundic : hence we fee that
the mineral principles are always, aétive, and forming new concre-
tions; and likely this activity is in proportion to the mineral and
metallic felts which the foffil contains : here the yellow-mundic
was moft adtive, as conlifting .of more felt than the plate-mundic;
but the brown-mundic has more felt ftill than the yellow, and will
divide and fall in pieces commonly in any moift place, and ihoot.
° By a letter ■ from Dr. J. Andrew, from Leyden, 1738.
forth
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