C 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 reverled, which fometimes 

 may happen. The natural form and bignefs of 

 the glais matraffes is feen tab. i, fig. 4. They 

 ought to be very thin at the bottom, that they 

 may not crack, by being iuddenly put over the 

 fire, or taken off it. In thefe matraffes folutions 

 may very eafily be made over the flame of a candle : 

 every mineral body capable of being affected by 

 the acids in this degree of heat, may here be dif- 

 folvcd, and particularly the metals. As the ma- 

 nagement in thefe procefies 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 publifhed ; 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 inflrument is likewife neceffary 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, floping 

 down from the fides 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. 1. fig. 5. it is 



com- 



