MricroGRAPHtIAs - 69 
more diftinét, the further ¢ de f is femoved from the trajecting hole; 
» So that'ipon the whole; we thall find that the reafon of thé Phenome- 
wafeems to depend upon theobliquity of the orbicular pulfé,to the Lines of 
Radiation,and_in particular,that the Ray ¢ d which conttitutes thes¢ar* 
fet hasitsinner parts, namely thofe which are next to the middle of the - 
Juminous body, precedent to the outermoft which‘are ‘contiguous to thé 
dark and wrradiating fkie.>: And that the Ray ef which pivesa Ble, has ° 
itsoutward  part,namely; that which is:contiguousto the dark fkie'prece* 
dentto the pulfe from the innermoft, which borders ot the bright arca 
of the luminous body: 5» 4 io s10q bofotler odi guisd Vi 2 
> Wemay-obferve further;that the caufe of the diluting’ of the colotirs to: 
-wards the middle,proceeds partly from the widenels of the hole throug} 
which the Rays pafs, whereby the Rays from feveral’ parts of thé lumi- 
nous bedys fall upon thany of the fame parts between ic and fas is moré 
manifeft by the Figure’: And partly alfo from the natute of the refraction | 
tfelf, for the vividnels or ftrength of the two terminating colours, arifing 
chictly asiwe have feen; from the very great differenve that is betwixt the 
outfides of thofe oblique undulations & the dark Rays circumambient,and 
that difparity betwixt the approximate Rays,decaying gradually : the fur- 
‘ther inward toward the middle of the luminous body they are-remov'd, 
the more muftthe colourapproach toa white or anundifturbed light. © 
+ Upon the calculation of the refraction and reflection from a Ball of 
Water or Glafs,we have much the fame Phenomena nately, an obliquity of 
the undulation in the famémanner as wé have found it here. Which, be- 
caufe it is very much to our prefent purpofe, and affords fuch an Inftiine 
-crucés, asnoone that I know has hitherto taken notice of, Ifhall fitther 
-examine..| For it does very plainly and pofitively diftinguith, and thew, 
-which of the two Hypothejes,cither the Cartefiaz or this is to be followed, 
by affording a generation of al! the colors in the Rainbow,whete accord- 
ing to the Cartefian Principles there fhould be none at’all generated. ‘And 
fecond]y, by affording an inftance that does more ‘clofely confine the 
caufe of thele Phenomena of colours to this prefent Hypothefis.°2 9 
And firft,for the Cartefan,we have this to obje& againft it, That whereds 
he fays (Ateteorum Cap.8.Sett.5. Sed judicabam unicamrefractioné feilicet ) 
ad minimi requiri,@» quidem talem nt ejus effeétus alia contratia (refraGi- 
one non defiruatur : Nan experrentia docet fs fuperficies NM & NP ( xempe 
refringentes) Parallele forent, radios tantundem per alteram iterum erettos 
_ghantum per unam frangerentur pullos colores depituros, This Principle df 
his holds true indeed in a prifme where the refraéting furfaces are’plain, 
-but is contradicted by the Ball or Cylinder, whether of Wate or Glafs, 
‘where the refracting {urfaces are Orbicular or Cylindrical. For if we ex- 
- amine the paflage of any G/obule or Ray of the primary Iris,we hall find . 
it to pafs out of the Ball or Cylinder again; with the fame inclination and 
3 refraction that it enter-d in withall, and that that Jaft refraction by ‘means 
Of the intermediate reflection fhall be the fame as if without any 
= Ses, at all the Ray had been twice refracted: by tW6’ Parallel 
a ae i) ela 
if Z 
es 
