This Image or Spectrum P T-was coloured, being red at its leali refracted end T, and vio~ let at, its molt refracted end'p, and yellow green and blue in the intermediate Spaces. Which ac ees with the firft Propofition, that Lights which differ in Colour do alfo differ in Refrangibility. The length of the Imagein the foregoing Experiments I meafured from. The fainte?: and outmofl red at one end, to the faintell and outmoft blue at the otheriend, ex cepting only a little Penumbra, whofe breadth fcarce exceeded a quarter of an Inch, as was faid above.