[ 292 ]• 
then to be direfted on the matter itfelf, and iif 
the fait fpreads too much about, leaving the proof 
almoft alone, it may be brought to it again by 
blowing the flame on its extremities, and direct- 
ing it towards the fubjedl of the experiment- 
In the aflays made with this fait, it is true, we 
may find’ if the mineral bodies which are melted 
with it have been difiblved by it or not ; but we 
cannot tell with any certitude whether this is done 
haftily and with force, or gently and flowly 
whether only a lefs or a greater part of the matter 
has been diffolved nor can it be v/ell diftinguilhed 
if the matter has imparted any weak tindure to 
the flag •, becaufe this fait alv/ays bubbles upon 
the charcoal during the experiment, nor is it clear, 
when cool; fo that fcarce any colour, except it. be 
a very deep oiie, can be difcovered, although 
it may fometimes be coloured by the mattenthat 
has been tried* 
SECT. XXL 
The other two falts, viz. the Borax, and' the 
Sal fufible microcofmicum, are very well adapted 
to thefe experiments, becaufe they may by the 
flame be brought to a clear uncolbured and tranf 
parent glafs ; and as they have no attradlion to 
the charcoal, they keep themfelves always upon 
it in a round globular form. The Sal fufibile mi- 
crocofmicum is very fcarce, and perhaps not to 
be met with in the fhops *, it is made of urine : 
Mr. Margraff has given a full account of its pre- 
paration in the Memoirs of the. Academy o£ 
Sciences at Berlin. 
SECT. 
