C 'i77 ] 
Vantage^ as far as pofTible, fuch a fyflerh miui be 
inore generally received, and at the fame time 
the eafier underftood, as it includes the mineral 
bodies in a lefs number of claiTes, orders, &c. by 
which the memory is not fo much clogged, as if 
billy their furfaces had been defer! bed, 
SECT. iV. 
This granted, let us corifider what difficulties 
there are to be met with in examining mineral bodies. 
Thefe are often like one another as to their external 
appearances^ although their conilitucnt parts are 
quite different, and ccnfcquently make them iife- 
ful in different ways : More part of them ought 
alfo to be changed from their natural form, and 
even often dffiblved, before they can be made any 
ufe of. Their figure and colour, or, in ffiort, their 
furfaces, are therefore not folely to be depended 
upon 5 we muff penetrate into them •, and they 
muff be decompounded according to the princi- 
ples of chemiftry. 
' SECT. V. 
By examining the mineral kingdom in this man- 
ner, we may now and then find the fiib;eds of 
our experiments (if even nearly the fame), to differ 
in fome of their effeds, v/hich is particularly owing 
to the difficulty of juftly determining the degrees 
of the fire employed ^ a difficulty not yet re- 
moved, but which, however, ought not to hinder 
us from going as far as poulbly we can, ffnee 
we find by pradlice, that fuch obftacles often are 
remedied by repeated experiments; and of thefe 
we never can make too many, if judicicufly per- 
formed. 
T 3 
SECT. 
