-vefcency with an Acid, and in this I was further confirmed 
by thefe two experiments. 
I found that if into a lolution of the Natron I pour'd 
an Acid:, while the water look'd whitifh or difturb'd the 
Salt not being perfectly diflblved it made a brisk fermen- 
tation : but when the water came to be clear,the Salt thea 
being perfectly diflblved, if I then poured an Acid upon 
it,it would not ferment: Ilikewife found that this folution 
being evaporated to a third part would ferment again. 
Its fecond principle I take to be an urinous Salt^ firft 
becaufe if mixt with fait of T^r/^^jr it fm ells like 6*«/ ^r- 
moniac when mixt with the fame Salt. 
Secondly, when it wasdiftill'd with fait of T^artar ix). 
a Retort, it afforded an urinous fpirit as piercing as the 
fpirit of Sal Armoniac. 
I come now to the rife of its principles S<2/ Marine and 
a Volatil Alkaly ; Sal Marine being a foflil Salt I fhall 
take for granted it receives from the earth and lhall en- 
deavour to illuftrate that it hath its Volatile Alkarly from . 
the air, firft becaufe its faid by Pliny, Spumam Nitri (which 
is the iVi3^^r^?;2 here fpoke of) Antiqui negabant fieri nifi 
cum ros cecidijjet. By MounfiQur de la Cbambre, it is affirm- 
ed that three or four days before the Nile begins to 
overflow, there falls a certain dew which hath a fermen- 
ting vertue, and leavens a paft expos d to the airland at 
that time faith Pliny, and Mounfieur de la Chambre the Ni- 
tre Pits grow full of Nitre. And&w^j'jF'^wyZ^^/^^j- and leveral 
fay, that tho yoo in a day die in GrandSairo of the Plague 
before the beginning of the inundation of Nile^yet the ve- 
ry day after 5 there does not one die, which doubtlefs could 
not proceed from any other reafou, then becaufe at that 
time, the air was impregnated with this Volatile Alka- 
ly, for at that time the M>/-^ Pits grow full and this dew 
falls: (this I think) may fufficiently hint to us the great 
ufe of its volatile fpirit efpecially in peftilential diftempers. 
Laftly, about that time that thcNile begins to or e flow 
thofe 
