( 4 ?<* ) 
wards ('as when the Prifm has one of its Planes laid flat to 
the Forehead,) then the blew Half of the Ribbon was lif- 
ted up, as at £ p • 
The Prifm was of white Glafs, having every Angle of 
60 Degrees : but when inftcad of it, one of a greenilh 
fort of Glafs, fuch as Objed Glafles of Telefcopes are 
made of, was ufed, having the refrading Angle which 
I look’d thro’ of about 48 Degrees ; the fame Phenome- 
non was more diftind, this Glafs having no Veins, but 
the Red and Blue were nearer to a (freight Line : in fuch 
manner that if A reprefent the Ribbon (een through the 
firft Prifm, B will reprefent the Ribbon feen thro’ the 
fecond Prifm, Fig. 1. if therefrading Angle of the laft 
Prifm had been as great as that of the firft:, the Light be- 
ing tranfmitted thro’ too great a Body of greenilh Glafs, 
the Phenomenon would not have (iicceededfo well. 
The blue Ribbon being (omewhat too pale, and the red 
a little dull ; 1 repeated the Experiment with a Skeen of 
blue, and one of red Worfted join’d together in the Mid- 
dle as the Ribbons were before ; and, the Colours of both* 
being very intenfe, the Experiment fucceeded better with 
both Prifms. All that were prefent trying the Experi- 
ment found it to fucceed, and that every Circumftance 
anfvver’d to the Account given in Prop 1. Theor. 1 . Book 1. 
of Sir Ifaac Newton’sOptics, as far as the Diredions there 
given were followed. So that it appear’d that the Blue, 
being carried lower than the Red in the firft cafe, and 
lifted higher in the (econd, was owing to the greater Re- 
fradion of the blue Ray : for tho’eaeh Part of theRibboa 
or Worded refleded all manner of Rays, yer the Pheno- 
menon was very apparent ; as alfo that the blue Ribbon 
or Worfted refleded the blue Rays more copioufly than 
the red Rays, and that the red Ribbon or Worfted refle- 
ded the red Rays more than the blue ones, becaufe the 
Red of the blue Half feen thro’ the Prifm was ie(s intenfe 
thaa 
