T ^iv ] 
liD be called’ Vitrefcenies cum akali, if their name 
was to have any connexion with their effects. 
Having now fo far overcome the former ig- 
saorance, v^hich was the foundation of the know- 
ledge for diftinguiihmg the mineral bodies into 
tranlparent or opaque, hard or foft, we prefer 
:the decifion of the fire, though we ftill labour 
funder the misfortune of not being able to mea- 
fure the degrees of .fire with fufficient accu- 
riacy ; for which reafon we always muft fuppofe 
plus ultra in the experiments by fire. 
Sand in reality is nothing elfe than very frnaU 
Hones ; therefore, if a feparate clafs were to be 
made of Sands, another clafs ought to be made, 
which fhould comprehend Gravel ; a third, 
Loofe Stones ^ and a fourth. Mountains : This 
would be a multiplicatio entium prater necejjiia^ 
ftemi a fault, which under thefe circumftances 
may eafily be committed, though not fo fooa 
perceived. 
The Saxa muft for the fame reafon be exclud^^ 
ed from any fyftem : Otherwife it would be the 
fame ,as if a botanift made a difference between 
die mifletoes, or fuch like vegetables, according 
to the different genera or fpecies of trees, plants, 
walls, or rails on which they grew. 
Petrefaftions, or Mineralia larvata^ confift 
pf fuch principles as ought to be deferibed in 
^heir proper places, without regard to their 
figures for which reafon they cannot be enu- 
merated a fecond time. The principal reafon 
for colleding them, is to acquire a knowledge 
pf fuch bodies of the animal and vegetable king- 
doms^ 
