62 
ee a other,muftnecefiarily be fomwhat more ebtumded,or impeded e 
MicrROGRAPHIA. 
trary of this will happen, if 17.and 18.be calculated in ftead of 16.and 17; 
both which does moft exactly agree with the Phenomena : For ifthe Sum, 
or aCandle (which is better) be placed about Ee, and the eye about — 
Pp, the Rays EF ef. at 16. and 17. will paint the fide of the luminous 
object toward 2 p Blue,and towards N P Red. But the quite contrary will 
happen when E F is 17. and ef 18. for then towards N P fhall bea Blwe, 
and towards #p a Red, exactly according to the calculation. And there 
appears the Blue of the Rainbow, where the two Blue fides of the two 
Images unite, and there the Ked where thetwo Hed fides unite, thatis, 
where -the two Images are juft difappearing 5 which is, whenthe Rays 
EF and NP produc‘d till they meet,make an Angle of about 41. and an 
half; the like union is there of the two Images in the Production of the 
Secundary Iris, and the fame caufes; as upon calculation may appears 
onely with this differénce, that it is fomewhat more faint, by reafon of the 
duplicate reflection, which does always weaken the impulfe the oftner 
it is repeated. | : 
Now, though the fecond refraction made at N~ be convenient,thatis, — 
do take the Rays glance the more, yet is it not altogether requifite 5 for 
it is plain from the calculation, that the pulfe dz is fufliciently oblique to 
the Rays K Nand &w,as wel asthe pulfe fcis oblique tothe Rays ¥ K & fk 
And therefore if a piece of very fine: Paper beheld clofe againft Nz and 
the eye look on it either through the Ballas from D, or from the other 
fide, as from B. there thall appear a Rainbow, orcolour d line painted on 
it with the part toward X appearing Red, towards O, Bive ; the fame alfo 
fhall happen, if the Paper be placed about K&, for towards T fhall ap- 
pear a Hed, and towards V a Blue, which does exactly agree with this m 
thefts, asupon thecalculation of the progrefs of the pulfe will 
ahi site prog p 
PARKS VR 23: : 
Nor do thefe two obfervations of the coloursappearing to theeyea- | 
bout? differing from what they appear on the Paper at N contradicteach | 
other ; but rather confirm and exa¢tly agree with one another, as willbe | 
evident to him that-examines the reafons fet down by. thé ingenious. 
Des Cartes in the 12. Seéf. of the 8. Chapter of his Meteors, where he | 
gives the true reafon why the colours appear ot'a quite contrary order | 
to the eye, to what they appear'd on the Paper if the eye be plac'din 
fteed ofthe Paper : And as in the Prifme, fo alfoin the Water, Drop, oF 
Globe the Phenomena and reafon are much the fame.) 59 fo 
Having therefore fhewn that there is fuch 4)propriety in the prifwe 
and water Globule whereby the pulfe is made oblique to. the progrefiive, 
-and that fo much the more, by how much greater the refraction is, I fhall | 
in the next place confider, how this conduces tothe production of co- q 
fours, and what kind of impreffion it makes upon. the bottom of the eye} 
and to this end it will berequifite to examine this Hypothefis alittle more 
_particularly. |. 
_ Firft therefore, if we confider the manner of the progrefs of the pul, 3 4 
it will feem rational to.conclude, that that partior end ofthe pulfe which =| 
by | 
