Spectrum analysis : six lectures, delivered in 1868, before the Society of Apothecaries of London / by Henry E. Roscoe ; with appendices, coloured plates, and illustrations.

Date:
1869
Catalogue details

Licence: Public Domain Mark

Credit: Spectrum analysis : six lectures, delivered in 1868, before the Society of Apothecaries of London / by Henry E. Roscoe ; with appendices, coloured plates, and illustrations. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    the rays passed through it, and different inclinations of the prism, to the horizon, made no sensible changes in the length of the image. Neither did the different matter of the prisms make any : for in a vessel made of polished plates of glass cemented together in the shape of a prism and filled with water, there is the like success of the experiment according to the quantity of the refraction. (After giving a rigorous proof that the rays in different parts of the spectrum are differently refracted, Newton proceeds.) This image or spectrum ri was coloured, being red at its least refracted end T, and violet at its most refracted end p, and yellow, green, and blue in the intermediate spaces, which agrees VAuth the first proposition, that lights which differ in colour do also differ in refrangibility. The length of the image in the foregoing ex- periments I measured from the faintest and outmost red at one end, to the faintest and outmost blue at the other end, excepting only a little penumbra, Avhose breadth scarce exceeded a quarter of an inch, as was said above. 1’kop. III. Theoe. 3.—The su'n's light consists oj rays differing in rejiexihility, and those rays are more reflcxible than others luhich are mo7’e I'ef'rangiblc. This is manifest by the ninth and tenth experiments, for in the ninth experiment, by turning the prism about its axis until the rays within it which in going out into the air were refracted by its base, became so oblique to that base as to begin to be totally reflected thereby ; those rays became first of all totally reflected, which before at equal incidences with the rest had suffered the greatest refraction. And the same thing happens in the reflexion made by the common base of tlie two prisms in the tenth e.xperimeiit.