186 NATURAL HISTORY 
being waffied away, the cryftalline parts, mixed with a flux proper 
to evaporate them, do not prevent the fuflon of the metal inclofed. 
As to the fhape of thefe cryftals, tin is faid to difpofe them to the 
quadrilateral pyramid figure w ; but this is not all, Nature has given 
us a greater variety of figures, but moftly geometrical, ftraight- 
lined, and angular, fo that indeed it is difficult to fay which figure 
this metal covets moft ; this we may be fure of, that all metals 
vary the fize as well as figure of their mineral granules in propor- 
tion to their own, and the power and quantity of the ingredients 
connected ; thus, for inftance, in the cafe before us, tin-ore fhall 
be compofed of cryftal, fait, fpar, fulphur, and metals and femi- 
metals more than one, of all which the figure fhall partake, and 
be regulated, mixed, and qualified, according as the tin, which is 
the principal, is determined by the feveral fubordinate concretions 
intermixed ; nor let it be thought by the reader fanciful and unpre- 
cedented to take notice and exhibit here the feveral ffiapes of tin 
and other metallic ffioots. The greateft Naturalifts have not thought 
them unworthy their notice. Dr. Tancred Robinfon obferves in his 
MS. Itinerary of Italy (fays Mr. Ray of the creation, page 94) 
the wonderful diverfity of fhapes and colours that oars and other 
foflils ffioot into, refembling almoft every thing in nature, for which 
it feems very difficult to him to affign any caufe or principle ; in the 
pyrites alone, he believes he himfelf may have feen, at home and 
abroad, above a hundred varieties.” I fhall therefore proceed in 
the fame manner with all our foflils, as I have done with the mun- 
dic or pyrites before, (page 137, fife.), and fet forth, in their 
natural fize, the feveral ffiapes of tin-grains, or cryftals inclofing 
tin, found in our Corniffi mines. 
The following figured tin-grains have occurred to me, and are 
exhibited in the annexed Plate. 
Fig. 1. Is a comprefled oblate pyramidal tin-grain of a refinous 
colour and texture. 
11. Side-view of a black tin-grain indented in the centre. 
in. Front of the fame, the apex towards the eye, with a 
perfedt rhombus in the middle indented, regularly lifted round 
the edges ; from two angles of the rhombus, the lift is only conti- 
nued along two of the four ridges which diverge from the central 
point. 
iv. Ten inclined planes, quadrangular, triangular, and hexago- 
nal ; black ; compofing all together one complete figured tin- 
grain. 
v. Irregularly quadrangular planes, the furiaces larger in the mid- 
w Woodward’s Cat. vol. I. page 220 . 
die 
