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Paper the ninth contains two Stones of fuch pure 
Loads, in which obferve the one is black, and the other 
nearly white. 
Thefe Cryftals concrete fometimes into the Form of 
a Parallelipepidon, whofe Summit is covered by a 
Pyramid ^ fometimes the Angles formed by the Sides of 
the Pyramid, and fometimes the Summit of the Pyra* 
mid are as it were plained away. 
Paper the tenth contains feveral of thefe Cryftals, of 
which Number the firft contains a whole Cryftal, which 
has none of its Angles off. ( See Flate the zd. Fig . 
the 8 th.). The fecond contains a Cryftal which has 
only two of its Angles plained away. (Fig* the yth(). 
The third contains a Cryftal which has all its Angles 
plained away. (Fig. the 10 th.). The fourth contains a 
Cryftal which has all its Angles and its Summit plain* 
ed away. (Fig. the n th,) 
Sometimes the Cryftals reprefent two equal pentela* 
teral Pyramids joined at their Bafe, 
As in Paper the eleventh, which contains two Clufters 
of Cryftals, which considered feparately are of that Form* 
Under whatfoever Form thefe Cryftals (hoot, they 
always carry an exceeding fine Surface } which, when 
rubbed off, can be renewed by no Art. In Paper the 
fourth one Side of the Parallelipepidon is rubbed 
away, to fhew its Appearance after lofing its natural 
Surface. 
Thefe Cryftals are of different Colours from the 
White (like white Sugar candy’d) to the deep Black. 
Thus Paper the twelfth contains a groupe of fmall 
white Tin Cryftals, which are very uncommon. Thefe 
white Cryftals feem to me to carry a finer Luftre than 
any other I ever faw, and are perfe&ly tranfparent • fo 
T 1 1 2 that 
