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The Refiduum they melt three times over, which 
always yields new Metal. They make here 
about 800 Center % per Annum, which is fold from 
fifty-three to fifty-fix Imperial Gouldens per Center. 
They find fometimes the black and fometimes the 
white cryftal Mineral in Nefts, or Clutters : The 
Stannum Toledrozi Nigrum is a very pure and rich 
Tin Ore -: They fay the white is rich alfo, but 'tis 
fo hard and difficult to melt, that the Tin is burnt 
to an Afh before it can be brought to Fulion. 
Near Geffries, mBarezth, they boil Vitriol. The 
Mineral from which they make it, is a black Schiftus , 
fome of it too is brown. It has fcveral fmall Veins 
of Pyrites in it. \Y hen firft taken out of the Pits it 
has no Tatte, but after it has been expofed fome 
Time to the Weather, and begins to moulder, it 
acquires a very fharpe Tatte. It is laid in great 
Heaps, under which there are Citterns for receiving 
the Water that runs from it after Rain, or that they 
pump upon it when the Weather is dry. This 
Water is conveyed by Conduits into the Boiling- 
Houfe, where there are two Leaden Kettles, in which 
it is boiled to a ftrong Ley, and then let off into 
Receivers where ic {hoots. Thefe two Kettles make 
from eight to nine hundred Weight per Week, 
which is all wrought by two Servants : It not having 
been found neceffary to add any new Mineral to the 
Heaps thefe fifteen Years patt, as they affured me. 
But as the Quantity of the Mineral confumed in that 
Time is not known, it is impoflible to determine 
how much of this Salt has been fupplied by the Air. 
They only add to the Quantity half an hundred 
Weight of Iron, which is confumed in the Kettles 
F f 2 - every 
