C 901 ) 
(landing afford no Tin&ure whilft fecluded from the 
Air : This was made to me very plain and clear, for ha- 
ving found out a way to feparate a white fiimy fub- 
ftance out of our clear Liquor, I then deftroy'd the Ex- 
periment, fo that when expos'd to the Air the Men- 
ftruum would no more give the lead Tin&ure : For a far- 
ther confirmation, this white Saline Subftance being in 
a fmall quantity diffolved in any proper Urinary Men- 
ftruum exhibits the Experiment fet down to advantage^ 
and gives a much finer and brighter Colour than what is 
drawn from Crude Copper, or from the Sulphureous 
parts : But fince the method above is more feafible, I 
will not fpend time for fear of difcouraging the Under- 
taker of an Experiment, to fet down this very elaborate 
method of .procuring the Salt of Venus. 
The great Iatereft the Air has in this Experiment 
made me think of applying it to the great change that 
is made upon Blood ; for it is obvious to every Body 
that there is a great difference in Colour betwixt the 
Venal and Arterial Blood, the Venal fo foon as it is let 
out of the Vein is obferved to be of a dark Complexion, 
and requires fome time to be expos'd to the Air before 
it obtains a florid Red, and that only Superficies which 
is contiguous to the Air, does for a good while become 
Red ; for I have turn'd up a Cake of Blood twenty four 
hours after it had been let out, and found it of a very 
dark and opake Colour, but the Air has immediately 
given it a bright and florid Red Tinfture. This fo ma- 
nifeft a change made by vertue of the Air is obvious even 
Lifpis& Tonforibus, which would make one wonder to 
find great Philofophers and Anatomifts endeavour to af- 
fign more for reign and ambiguous Caufes of fo demon- 
ftrable an effeft of the Air. Thus our Famous Anato- 
mifts Dr. Highwore, and Dr, NeeSam, and others, have 
adventur'd to do ; who would have refpiration to be 
chiefly to promote the Circulation of the Blood, and that 
C c c great 
