A Letter from Mr. Charles Leigh of Brazen- Nofe 
College in Oxford, to Dr. Rob* Plot Diredor of 
Experiments to the Philofophical Society of Ox- 
ford , and one of the ^'ecretaries -of the Royal 
vSbciety* 
Sill. 
Since you gave me fome fpecimens of the waterof La^ 
iron, and likewife oi Nttrian Nitre, I have found 
that thofe Defcriptions which the Antients give of it, 
exadlly agree with thofe Ipecimens we have here ; their 
encomiums of it were fo many, but fo different the names 
which they afcribed to it, as a fceptic indeed mighc e- 
qually queftion whether or no they writ of any thing 
elfe, or whether or no they writ of any fuch thing. 
That we might therefore the better underftand the wri- 
tings of the Antients concerning itj and the Thcenomena 
which it afforded here, I have thought convenient to 
make uleof this method. I fhall in the firft place fhew 
whence Nitre has its denomination. Inthefecond, the 
different names which ancient Authors afcribe to it. In 
the third, the different places whence it comes. In the 
fourth, a defcription of it as it is when a Compojitum. In 
the fifth, the number of its principles when chymically 
refolved. Inthefixth, the rife of them. In the feventh, 
its feparation from rhe water of Latron. in the eighth, its 
ufe inPhyfick. In the ninth,inAgricultureandMechanicks. 
In the tenth, wherein it differs from ^S'*^^-^^^^^^'^^. In the 
eleventh, from Salt-Petre. 
That all iV^>r^ took its name from a Town in ^gypt: 
called A%r/^, I fhall take for granted ; I fliall there tore 
in the next place give you an account of the different 
names, which by Authors are afcrib'd to Nitre. 
D 2 By 
