( 537 ) 
tore of thofe raies , whieh according to their degrees of refraji*' 
gibility are difpofed to exhibit a Yellow and Green colour; 
which he declares by the inflance of thofe two ?&wdtn mixu 
Now , whether this Hypothefis, or Mr. fl^^^^'s, or that of Def- 
ar/^/s,orthe^ifi>«?//2V, may be moft favoured hereby, I leave as 
an Inquiry ^ viz, Whether Colour is moft referable to thepre- 
difpofitionof the Raies and internal textures or the concave fur- 
face of the refraftingandrefleSing Air ; or to the furface of the 
body, which diverfly modifies the Corpufcles or Raies of 
light. 
But ia rwy (!tnple judgment, thebufinefs will not bear a contro- 
verfie, fince each of thefe maj^ have^ nay certainly has a diftinfl: in- 
tereft in the phaenomena of Colours, and the lofing of the blew for 
tranlparenf, and regaining it again by the Air^s re admiffion, feems 
to countenance the intcreft of the Air, which may be altered by lo- 
fing feme parts in operating on the Solution. The obviating of 
theobjeftionof the powder remixt fo regaining the colour,fliows 
atoncc the ingenuity of the Author in taking notice of it, and the 
infufficiency of the ObjeSion it felf to challenge theefFeft from the 
Air. The mild operation of Spirit of Vinegar on mim»m, may noc 
change the Air's fpring, by extricating fpringy air out of the Vi- 
_ negar to fupply that it had imbibed, as it did an elaftical fubftance 
in the notes. The Hi^erfity uf theoperation of 5*^/ Armoniac might 
be refer'd to the ftrength of the Spirit ; fo may the quick- 
imfs and length of retaining the colour and flownefs of lofing it ; 
the wcaknefs proceeding from the Air imbib'dj or dividing fome 
of its particles to extrude them, as I noted before : In al l which, 
eritical times and qualities may beeoncern'd, which my weaknefs 
cannot examine i but hope, thefe Obfervat ions, as that Honourable 
perfon's Experiments, will give rife to further inquiries. 
Thofe Ingenious Frm^«?^;^, excited by Mr.B(?y<f,che Glory of 
Learning, as well as of our Nation, having given us an attempt of 
mixing and fermenting liquors i;^^^^a,do profecuteFernientationj 
particularly of that in the growth of plants 5 how ic may be im* 
peded or promoted by the abfence or prefence of the Air. As for 
their taking the Receiver off from the Engine, I fuppofe, it couid 
not be fljaken but in the very moving fome Air mufl: get in , not 
fomuch^ as fenfibly to raanifeft it felf in the Mercury, though fuf- 
ficienr 
