MicROGRAPHIA, 
the fame effe@ : only where the Light is brighteft, there the Coloutsate _ 
moft vivid. So does the light of a Candle , collected by a Glafs-ball, 
And further , it is all one whatever fide of the coloured Rings, be to- 
wards the light ; for the whole Ring keeps its proper Colours from the 
middle outwards in the fame order ee re related , without varying 
at all, upon changing the pofition of the light. i 
But sho all Ge mal ebieresEe that here are all kind of Colours 
generated in a pelucid body,where there is properly no fuch refraction as 
Des Cartes fappofes his Globules to acquire a verticity by: For in the 
age and even Plates it is manifeft, that the fecond refraction ( accord- 
gf to Des Cartes his Principles inthe fifth Section of the eighth Chapter 
his Meteors) does regulate and reftore the fuppofed turbinated Glo- 
/es unto their former uniform motion. This Experiment therefore will — 
prove fuch a one as our thrice excellent Verulam calls Experimentum Cru- 
cis, ferving as a; Guide or Land-mark , by which to dire¢t our courfe in 
the fearch after the true caufé of Colours. Affording us this’ particular 
negative Information, that for the production of Colours there is not ne- 
ceflary either a great refraction, as in the Prifme nor Secondly, a deter 
tination of Light and fhadow , fuchas is both in the Prifme and Glafs- 
ball. Now that we may fee likewife what affirmative and pofitive Inftrus _ 
Gion it yields,it will be neceflary, to examine it a little more particularly 
and ftri¢tly 5 which that we may the better do, it will be requifite to 
erg fomewhat in general concerning the nature of Light and Refra: 
10n. 9 i 1900 i 3 
And firft for Light, it feems very manifeft, that there isno luminous Bos 
dy but has the parts of it in motion more or lefs. ined: a a 
Pirft, That all kind of fiery burning Bodies have their partsin motion, — 
I think, will be very eafily granted me. That the fpark ftruck froma 
Flint and Steel is ina rapid agitation, [ have elfewhere made probable. _ 
And that the Parts of rotten Wood,rotten Fifh,and the like, arealfoin mos _ 
tion, I think, will as eafily be conceded by thofe,who confider,thatthofe _ 
parts never begin to fhine till the Bodies bein a ftate of putrefaction; _ 
and that is now generally granted by all, tobe cauféd by the motionof _ 
the parts of putrifying bodies. ‘That the Boxonian ftone fhines no lon _ 
ger thenit is either warmed by theSun-beams, or by the flame of a Fire 
or of aCandle, is the general report of thofé that writelof it; andof — 
others that have {een it. And that heat argues a motion of theinteinal — 
parts,is ( as I faid before ) generally granted) i) 
_Butthere is one Inftance more 5 which wasfitft thewn tothe Royalso> 
ciety by Mr. Clayton a worthy Member thereof, which doésmakethisAb 
fertion more evident then all the reft: And thatis, That'a Diamond bes — 
Ing rab'd, firuck, ot heated inthe dark, fhines for a pretty while after, {0 
long as that motion, whichis imparted by any of thofé Agents, remains 
(in the fame manner as a Gla&,rubb’d,{truck,or(by a means which I fhall 
elfewhere mention’) heated, yields a found which lafts aslong asthe o#= 
brating motion of that fonorons body ) feveral Experiments made om 
which Stone, are fince publifhed in a Difcourfeof Colours; bythe truly 
: honou- _ 
