:l8 6 N A T U R A L H l S T -C P R Y
being walhed away, the cryftalline parts, mixed with a flux proper
, .tb^vapbrate them, dp not prevent 'the fufión of the metal iriclofed.
As to the fliape o f thefe-cryftafe, l-tin is. faid tO difpofe them to the
quadrilateral pyramid figure’ ; but this is not all, Nature'-has given
us a greater variety of figures, bht taoftly geometrical, ftraight-
. lined, and angular, fo that indeed it is difficult to fay which figure
this metal OQvêts rniofl: ; this we may bè fure of, that all metals
vary the fize as well" as • figure of their miner#! granules in proportion
to their owh, and the power and quantity of the ingredients
'OcHme^ed j thti, for inftance, in thè tcaffe before us, tin-ore lhall
be cOmpofed rif ciryftal, fait, fpar, fulphur, and metals and femi-
metals more than One, o f all which the figure fhall* partake, and.
be regulated, mixed, and qualified, according as the -tin, which' ïs
the principal, is determined by the lèverai fubordinate concretions
intermixed ‘ tibr let it be thought by the reader fahciful and unprè-
cedfeiitefl to take notice and exhibit here- the feveral lhapes of ;fih
and other metallic Ihoots. The.greatcft Naturalifts have not thought
them unworthy their notice. Dr. Tancred Robinfon öbfëfves.In his
MS.. Itinerary o f ltaly (fays Mr. Ray of the creation, page 94)
the wonderful diverfity of lhapes and colours that oars and other
fulfils Ihoot into, refemhling almoft every thing in®Mfe,*for which
it feeötó Very difficult to him to afligri any caufe or principle? in the
pyrites" alone, ■ he. believes he himfelf may have feem at home and
abroad, above a hundred varieties.” I lhall therefore proceed in
thé feme "manner with all our foffils,. as I. hâve done with' the mun-
dic or pyrites before, (page 1^7, ■ \foitK?:;fii;;:^ ^ r
natural fize, the feveral lhapes of tin-grains, or cryftals inclofing
tin, found in our Coniilh mines. . : -....... -
' The following figured "tin-grains have Occurred to me, and are
• exhibited in the annexed Plate.
Fig. i. Is a coniprdfed oblate pyramidal tin-grain-of a refinous
colour and texture.
11. Side-view o f a black tin-grain indented in thé centre.
in. Front of the feme, the apex towards' the eye, with a
perfect rhombus in . the middle indented, regularly lifted round
the edges ; from two angles of the rhombus, the lift is only continued
along two of the four ridges which diverge from the central
"point.
' iv. Ten inclined planes,. quadrangular, triangular, and hexagonal
; black j cOmpofing all together one complete figured tin-
grain.
v. Irregularly quadrangular planes, the furfaces larger in- the mid-
* Woodward's Cat. vol. I. page 220.
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