Y, brillando el sol en mi oscura habitación a través de un pequeño agujero en la contraventana, coloqué dicho paralelepípedo en su haz a cierta distancia del agujero, en una postura tal que los ejes de los prismas pudiesen ser perpendiculares a los rayos incidentes, y que dichos rayos, al incidir sobre el primer lado de un prisma, pudiesen continuar a través de los dos lados contiguos de ambos prismas y emerger por el último lado del segundo prisma. Este lado, al ser paralelo al primer lado del primer prisma, hizo que la luz emergente fuera paralela a la incidente.
Then, beyond these two Prisms I placed a third, which might refract that emergent Light, and by that Refraction cast the usual Colours of the Prism upon the opposite Wall, or upon a sheet of white Paper held at a convenient Distance behind the Prism for that refracted Light to fall upon it. After this I turned the Parallelopiped about its Axis, and found that when the contiguous Sides of the two Prisms became so oblique to the incident Rays, that those Rays began all of them to be reflected, those Rays which in the third Prism had suffered the greatest Refraction, and painted the Paper with violet and blue, were first of all by a total Reflexion taken out of the transmitted Light, the rest remaining and on the Paper painting their Colours of green, yellow, orange and red, as before; and afterwards by continuing the Motion of the two Prisms, the rest of the Rays also by a total Reflexion vanished in order,