SECT. II. 
Shapes. 
i 9 6 NATURAL HISTORY 
When iron forms by dropping from roofs and fides of caves, it 
becomes a lump of tubular parallel ftems which hang fide by fide 
in the fame manner as the mundics, Plate xvi. page 141, Figures 
xxxiv, xxxv. and copper, Plate xxi. Fig. ix. and is called Brufh- 
ore. Sometimes it is found in the form and fize of mulket bullets ', 
Plate xx. Fig. xxxi. page 186, each of which is fixed in its nidus, 
but never detached and perfectly globular, as far as I have yet feen. 
Dr. Grew (Muf. R. S. page 332) mentions iron balls made by the 
rolling of iron-fand off the banks among the iron-mines near Sen- 
neck, efpecially after rain; but thefe here are natural from the 
mine. Sometimes it is bliftered into round tubercles, as Plate xv. 
Fig. ix. page 137, and Plate xxi. Fig. in. at other times made 
into the exadt lhape of a button, protuberant in the middle, and 
declining on every fide into a variety of polygonal planes, as Fig. 
xxx 11. Plate xx. In both thefe laft cafes it is called the Button-ore. 
Iron is laid to give the rhomboidal form to cryftals u : if this be true, 
it may allb do the fame to mundics ; but, as the rhomboidal form 
is not peculiar to iron, the queftion will ftill remain undecided, 
whether one and the fame mineral fait may not give this figure to 
them all, and be no more the proper confequence of iron than of 
the other fofiils. This ore is fometimes found in Cornwall, near 
Truro, confiding of parallel plates which break into very fhining 
and glofiy furfaces w , and a coarle falle kind of iron-ore, called Kal, 
is found in moft parts of Cornwall ; this laft promotes the fufion 
and toughnefs of tin, elpecially where mundic abounds ; for the 
mundic by itfelf will fcarce permit the tin in many places to be at 
all ducftile : the truth is, the Kal connects the metallic parts, 
whereas the fulphurs of mundic have a quite contrary effedl, and[ 
render them volatile. 
CHAP. XV. 
Of the Copper found in Cornwall. 
T HIS fupple, rich, and ufeful metal, Cornwall has for fome 
ages been reckoned to have been plentifully ftocked with % 
but it has never turned out any confiderable profit to the owners 
of the land till within thefe fixty years ; fo little does difcovery fig- 
nify, unlefs it be purified with application, and knowledge how to 
make the proper advantage of it. At prefent it may be aflerted 
- r As in Huel-an-boys, in St. Juft. w Woodward’s Cat. vol. II. page 86. 
u Woodward’s Cat. vol. I, page 220. Hill, x See Carew’s Survey, page 7. Norden, page 
page 197 - 9,41,42,104. 
with 
