[ 3*7 ] 
round the neck of the bottle ; and if this is nicely 
made, nothing can come through, though the box 
be inclined, or even reverfed, which lometimes 
may happen. The natural form and bignefs of 
the glafs matraflfes is feen tab. i, fig. 4. They 
ought to be very thin at the bottom, that they 
may not crack, by being fuddenly put over the 
fire, or taken off it. In thefe matrafies folutions 
may very cafiiy be made over the flame of a candle : 
every mineral body capable of being affedbed by 
the acids in this degree of heat, may here be dif- 
folved, and particularly the metals. As the ma- 
nagement in thefe procefTes is the fame as in ordi- 
nary laboratories, of which we have ample defcrip- 
tions in feveral books, it is not necefiary to copy 
them here, my intention being only to defcribe an 
eafy way of making experiments upon mineral bo- 
dies, which has not before been publirtied ; in ex- 
plaining of which I neverthelefs have been forced 
.now and then to mention fomething that more 
properly belongs to. Mineralogy. 
SECT. LXIV. 
Another iiiftrument is like wife neceflary to a 
complete Pocket-Laboratory, viz. a Wafhing- 
trough, in which the mineral bodies, and particu- 
larly the ores, may be feparated from each other, 
and from the adherent rock, by means of water. 
This trough is very common in the laboratories, 
and is ufed of different fizes •, but here only one is 
required of a moderate fize, fuch as twelve inches 
and a half long, three inches broad at the one end, 
and one inch and a half at the other end, doping 
down from the Tides and the broad end to the bot- 
tom, where it is three quarters of an inch deep ; 
I have given a figure of it in tab. i. fig> 5. It is 
com- 
