Spectrum analysis in its application to terrestrial substances, and the physical constitution of the heavenly bodies / Familiarly explained by the late H. Schellen. Trans. from the 3d enl. and revised German edition by Jane and Caroline Lassell.

  • Schellen, H. (Heinrich), 1818-1884.
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: Spectrum analysis in its application to terrestrial substances, and the physical constitution of the heavenly bodies / Familiarly explained by the late H. Schellen. Trans. from the 3d enl. and revised German edition by Jane and Caroline Lassell. Source: Wellcome Collection.

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    and this image will appear to be at the same distance from the prism as the luminous slit D when the prism is in the Position of minimum deviation. Instead of viewing the image D' of the slit with the naked eye, it may, like any other object requiring more minute inspection, be examined with a telescope. If, as in Fig. 22, a convex lens L is placed in the path of the emergent rays, which behave as if originating from the point D', then, in accordance with the laws of optics, these rays will be re-united at the point b. This point is the image of the luminous point D, and if a screen is placed at Fig. 22. Prism with Convex Lens. this spot, and the point D becomes a brightly illuminated slit, an inverted image of the slit will be formed at b. In these phenomena it is understood that the light proceeding from D is homogeneoLis—such as is produced by a faintly luminous flame of a spirit lamp when made 3'ellow' b}'^ the presence of common salt. If such a flame is placed in front of the slit D, or in front of a prism as in Fig. 23, and viewed through the prism, the deflected image of the slit or flame will be seen at the more elevated point D' ; if the prism is inverted, the rays will be deflected from above, and the slit or flame will be in a lower position. B3’ projecting