( 535 ) 
to bt extruded oue of theglafs, which leaving the other particles 
free from their preflTure , confequencly render them more ac li- 
berty, and lefsfpringy. And this may have an intereft inrarcfa» 
flion of the Air, by what caufe foever, as beat , cold, or taking a« 
way the ufual preffion^&c. 
I am not ignorant of what the excellent Author has delivered 
of the Impervioufnefs of Glafs to Air 5 but then he means the true 
fpringy Air, not that, which we fuppofe by its minurenefs to have 
loft its fpring, and the particles of the Air in relation to their 
refpefiive magnitude, may be compared to bullersj ftor, and fand 
mixt together : Or this corrofion may precipitate fome p^rt of 
the Air ; which opinion they would favour, who fuppofe its par- 
ticles Nitrous. 'Tisalfo eafie to think, that the Air being a Ren- 
dezvous of fo many Corpufcles, and confequently fo heterogene- 
ous a body, may bediyerfly qualified by admitting Fffluvk from 
folutions, which may remain unaftive , till they meet with forne 
body predifpofed to receive their operation ^ which, ignorance of 
the caufe, and unexpeSednefs of the event (feeing it did not afi 
on other bodies,) makes ftrangely admirable. 
In the Experiment , the folut ion may acquire a brown co- 
lour by the menjlruunis imbibing the particles of Copper into it 
felf, which would alter its texture; and the impeding panicles, 
diverfifying the refraftions and refledlions , may mbdifie the rays 
of light ; or, as it is in Mr, Nevptons Theory , the folution may be 
qualified only to admit fuch raies whofe degrees of refrangibi- 
Hty , and mixture with other raies, may be predifpofed to give a 
BfowD, (to flicw what mixture or refrafiion makes this parti- 
cular colour, I have not at prefent Mr. Newton's Theory by me ;) 
to which effefi: the Air did much contribute: But how far this 
and the following Experiments of the producing of Colours 
may countenance the ingenious Mr, Book's Hypothefis, of Colours 
being.niade by the various concave furfaceof the refiefting Air, 
I recommend to further inquiry. Nay, the Air may be much con- 
cerned in the folution it felf , fince ic is allowed to bean llniverfal 
mefsffiruum.ztkzfiof all Sulphureous bodies ; 
and I wifii it had been recorded f ; Whether ^ ^v.i/. ^nthr here 
that folution was not fomething fooner made in '-^«^«^ dtdiurpofdy for~ 
thefreeAir.than in the Glafs with the hermcticd ^^Zf^^^ 1 
titrare of the difficuln of determining it > 
floppie 
