E 31S ] 
commonly made of wood, which ought to be chofep 
fmooth, hard and compadb, wherein are no pores 
in which the minute grains of the pounded matter 
may conceal themfelves. 
It is to be obferved, that if any fuch matter is 
to be walhed, which is fufpeded to contain fome 
native metal, as filver or gold ; a trough Ihould be' 
procured for this purpofe, of a very fhallow dope, 
becaufe the minute particles of the native metal 
have then more power to afiemble together at the 
broad end, feparate from the other matter. . 
SECT. LXV. 
The management of this trough, or the man- 
ner of wafhing, which I fuppofe to be known be- 
fore, confifts chiefly in this : That when the matter 
is mixed with about three or four times its quantity 
of water in the trough, this is kept very loofe be- 
tween two fingers of the left hand, and Ibme light 
ftrokes given on its broad end with the right, that 
it may move backwards and forwards, by which 
means the heavieft particles aflemble at- the broad 
and upper end, from which the lighter ones are to 
be feparated by inclining the trough and pouring 
a little water on them. By repeating this procefs, 
all fuch particles as are of the fame gravity may 
be colledted together, feparate from thofe of a dif- 
ferent gravity, provided they all were before equally 
pounded ; though fuch as are of a clayilb nature, 
are often very difficult to feparate from the reft, 
which, however, is of no great confequcnce to a 
fkilful and experienced waflier. The wafinng pro- 
cefs is very necelTary, as there are often rich ores,^ 
and even native metals, found concealed in earths 
and fand in fo minute particles, as not to be dif 
covered by any other means. 
FINIS. 
