Of Light and Colours."

posed to be refleBed or transmitted., accorct-ing to the several Degrees of Thickness;

so

Plate

xxxvnr.

Fig- i.

f

from the touching Farts. He observed the Place wherethey touched became absolutely transparent, as if theyhad there been one continued Piece of Glass.

6. For when the Light fell so obliquely on the Plateof Air between the Prisms as to be all reflected, it feem’din that Place of Contact to be wholly transmitted, inso-much, that when looked upon, it appeared like a blackor dark Spot, by reason that little or no sensible Lightwas reflected from thence, as from other Places.

7. When he looked through the Prisms, this Place ofContact seemed (as it were) a Hole in the Plate of Air,and through this Hole Objects that were beyond mightbe seen distinctly, which could not be seen throughother Parts of the Glasses where the Air was interjacent.By harder Compreflion, the Spot was dilated by the yield-ing inwards of the Parts of the Glasses.

8. When the Plate of Air, by turning the Prismsabout their common Axis, became so little inclined tothe incident Rays, that some of them began to be trans-mitted, there arose in it many slender colour’d Arches,which at first were shaped almost like the Conchoid, asin Fig. 1. and by continuing the Motion of the Prisms,these Arches increased and bended more and more aboutthe said transparent Spot, till they were compleated intoCircles or Rings encompassing it; and afterwards con-tinually grew more and more contracted.

9. These Arches and Rings became tinged with va-rious Colours, as the Motion of the Prisms was conti-nued, being at first of a Violet and Blue ; afterwards o*a White, Blue , Violet ; Black , Red , Orange , Tello zf.White , Blue, Violet , &c. After this, the colour’dcontracted, and became only black and white: s ^Prisms being farther moved about, the Colours all be-gan to emerge out of the Whiteness, and in a contraryOrder to what they had before.

10. But to observe more nicely the Order of t 'Colours which arose out of the white Circles, as tRays became less and less inclined to the Plate of Ts’

2 ‘