| Description | ' Mr Newton's Experiment which had been disputed by mr Llinus and hi Fellowes at Liege was tryed before this Society, according to the directions of the said Mr Newton, and succeeded as he all along hath asserted it would do. And it was Ordered, that the Secretary should signifie this successe to those of Liege, who formerly had certified, that if the Experiment were made before this Society, and succeeded according to Mr Newton's assertions, they would acquiesce; as appears by Mr Gascoines letter written to Mr Oldenburg December 15 1675.
The Experiment was thus: A prisme was taken and so held, that its axis was perpendicular to the Suns Rayes (it bing a very clear Sun-shiny day) and in this posture it was placed in a darkened Roome, as close as might be to the hole, through which the Sun shined into the dark roome, which hole, was about the bignes of a pease. Then the Prisme was turned Slowly about its axis, and the colours were seen to move upon the opposite Wall first towards that plaace to which the Sun's direct light would passe, if the Prisme were taken away, and then back againe. When the colours were about the midle of these two contrary positions, that is, when they were nearest to that place to which the Suns direct Ray tended, there the Experimenter stopped, the Rays being then equally refarcted on both sides the Prisme. In this posture of the Prisme, the figure of the colours being observed, it was found not round, as Linus contends, but oblong; the colours Red, Yellow, Green, blew, purple, succeeding in Order, not from one side of the figure to the other, as in Mr Linus his conjecture, but from one end to the other and the length of the figure being not parallel, but transvers to the Axis of the Prisme. ' |