[ 315 ]' 
upon the fubjeft ; which is very convenient when 
there is no opportunity, nor time, of ufmg this in- 
ftrument. 
SECT. LVIII. 
The Gypfa, which confifl: of lime and the vitri- 
olic acid, ( Sed. xviii. 12.) are not in the leaft at- 
tacked by the acid of nitre, if they contain a fuffi- 
cient quantity of their own acid, becaufe the vi- 
triolic acid has a ftronger attradion to the lime, 
than the acid of nitre : but if the calcareous fub- 
ftance is not perfedly faturated with the acid of 
vitriol, then an effervefcence arifes with the acid 
of nitre, more or lefs in proportion to the want of 
the vitriolic acid. Thefe circumftances are often 
very effential in diftinguifhing the calcarei and 
from one another. 
SECT. LIX. 
The acid of nitre is likewife neceffary in trying 
the zeolites, of which fome fpecies have the fin- 
gular effed to dilTolve with effervefcence in the 
abovementioned acid •, and within a quarter of an 
hour, ^or even fometimes not until feveral hours 
after, to change the whole folution into a clear 
jelly, of fo firm a confiflence, that the glafs, wherein 
it is contained^ may bereverfed, without its falling 
out. 
SECT. LX. 
If any mineral body is tried in this menftruum, 
and only a fmall quantity is fufpeded to bedifiblved, 
though it was impoffible to diftinguifh it with the 
^ye during the folution, it can be eafily difcovered 
by 
