( ^ J 
Problem, of which I have now neither time nor conve" 
nlency enough to deliver my Thoughts. And by what 
has been (aid, I hope it does already (eem fuiHciently pro- 
bable, that the way above propofed may prove of good 
u(e, both to Navigators, that are often neceffitated to 
Water in unknown places, and to others that only, or 
frequently drink that Liquor, without having any better 
way than the Tafte, (which is but an incompetent one) 
to elutriate its Frefhncfs and Saltnefs by *. 
XII. Fourthly, (and Laftly) tho' 
both in my Letter to Dr. /. B. and 
in this prefent Pofiicript, I did not 
for certain Reafons afcribe to our 
Method of examining Waters, a 
greater Nicety than to be able to 
difcovcr one part of Salt in a thou- 
fand of Water, that Proportion be- 
ing great enough to recommend it, 
and exprefsd by a round number 
eafie to be retain'd in ones Memory: 
Yet I would not have it thought 
but that, if it were requifite, our 
Method may make more nice Di£ 
coveries. For, having fometimes 
for Curiofities fake, put one Grain 
of Salt into no lefs than Fifteen Hun- 
dred of diftilled Water, we could 
manifeftly, (tho' not quite Co con- 
fpicuoufly as before) make it appear 
by our way, that even this fo light- 
ly impregnated Liquor was not de- 
void of Salt, but had more of that 
in it, than fome of the Patentees 
Water that I kept by me had ; nay, 
I once found, that a Grain of dry 
Salt, being difperfed through two thoufand, and another 
time 
* XL I might add on this occafion, 
That, whereas Experience has inform'd 
federal Perfons who have confulted it, that 
divers Medecinal Waters, that are pre- 
fum'd to owe their Venues to the partici- 
pation either of Metalline, or of other 
Mineral Bodies, do upon trial appear to 
leave fometimes little, and fometimes no- 
thing behind thcm,except a kind of com- 
mon Salt ; our Precipitant may much 
aflift Men to difcovcr, whither a mineal 
Water propos'd to be examin'd, do, or 
do not contain, fuch a Salt ; and if it do, 
-whether it contain it ccpioufly or no. 
This I have try'd upon more than one of 
our Englifh mineral Waters, and there- 
by found in a trice, that one that is re- 
puted of another nature, eonrain'd pretty 
ftore of Saline matter \ and that another 
(which is ftill, for ought I have learn'd, 
of an unexamin'd and unknown Nature ) 
is impregnated with a furprizing Plenty 
of Sakifh Subftance. But how and with 
what Cautions, our Precipitant may be 
the moft ufcfully employ'd, about the Ex- 
-amen of medicinal and other mineral 
Waters, belongs not to this place, ( but 
to || another Paper.) Upon which -account 
I forbear to declare the ufe I have fome- 
times made of our Precipitant, in esami- 
■nirig thefrefh Urine of Men, the Serum 
of Huma ne Blood, and other Bodies be- 
longing to what the Chymifts call the 
Animal Kingdom. 
jj About the Ex men of Mineral Waters. 
