la the fecond place^ I told yQU^that the Objeetorsf^j?^/^^/^ 
as to the fundamental part of it is 
that the moB free and genume con^ ^ot againit me. Iliat tundamental 
Bitutimbtf that and all other MechS' SuppoiltiOD IS > That the .parts of 
totr^^^^^^'^'' to my bodtes, when briskly agitated, da ex- 
cite Vibrations in the Mther^ iphicb are 
propagated every way from thofe bodies in [Ir eight lines ^ and caufe a 
Senjation of Li^h4y beating and daping againji the bottom of the 
Eye^ [omething after the manner that Vibratims in the Air caufe a 
Sejjjation of Sound by beatingagainjl the Organs of Hearing. Now, 
themoft free and natural Appiieation ot this Hypothecs to the 
Solution ofphcemmena I rake to be this ; That the agitated parts 
ofbodieSj according to their feveral fizes^ figures, and mo^ 
tionSj doexcite Vibrations in the cether oi various depths or 
bigneffeSjWhich being promifeuoufly propagated through that 
Medium to our Eyes,effed: in us a Seufation of Light of a White 
colours butifby any means thofe of unequal bignefles be fe-- 
parated from one another, thelai;geft beget a Senfationofa 
.K^^colour^ the leaft or fliorteft, oi adecpFiolet^ and the in- 
termediatones, of iotermediat colors ; much after the man- 
ner that bodies , according to their feveral fizes, fliapes, and 
motions^ excite vibrations in the Air of various bfgneffes, 
wbichj according to thofe bigaeflfes, make feveral Tones in 
Sound: Thattht largeft Vibrations are beft able to over- 
vcometherefiftanceof a Refraaingfuperficies, and fo break 
through it with leaft Refraaion 5 whence the Vibrations of 
^ feyeral bigneffe$3 that is^ the Rays of (everal Colors, which 
are blended together in Light, muft be parted from one ano- 
ther by Refradion, and fo caufe the Phcemmena o{ Pr?fmes2Lnd 
other refrafting fubftances : And that it depends on the thick- 
nefs of a thin tranfparen-t Plate or Buble, whether a. Vibration 
lhall be r^^^S^^ at its further faperficies^or ifr^^^/raV^^^i^ fothat, 
according to the number of vibrations, interceding the two 
fuperficies^they may be re9eaed or traDfmitted for many fuc- 
ceffive thicknelFes. And fince the Vibrations which make 
Blew and Fiolety are fuppofcd (horter than thofe which make 
RedandTel/orv^ they maft be reHefted at a lefs thickncfs of the 
Plate ; Which is fufiicient to explrcate ail the ordinary ph^n@s 
rrj.-^^ of thofe Plates orBubks^ and affo of all natural bodjei. 
