Scientific memoirs : being experimental contributions to a knowledge of radiant energy / by John William Draper.

  • Draper, John William, 1811-1882.
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: Scientific memoirs : being experimental contributions to a knowledge of radiant energy / by John William Draper. Source: Wellcome Collection.

    451/488 (page 447)
    absorbing trough was not used. Though the sun's rays were not°brilliant, the chloride at once melted, forming a reddish-looking liquid. It was kept in that condition all day. When cool it proved to be in the state of horn-silver, easily cut by a knife. When the rays fii'st touched it a fume was disengaged, due probably to the escape of vapor of water. It seems, therefore, that this substance when perfectly dry is not decomposable by sunlio-ht thono-h so sensitive at common temperatures when moist. In Fig. 95, a is the platinum crucible; 5, the place of the material experimented upon, re- ceiving at the focus the converg- ing rays, g. I must refer to the original Memoir for the detail of numer- ous experiments on many metal- lic compounds, the general re- sult of these being that, no mat- ter how brilliant a ray may be, it cannot carry a decora- position farther than a feeble one acting for a corre- sponding longer period of time could do. Compounds that can resist the foi'ce of an ordinary ray cannot be broken down by the intense illumination of the focal point of a burning-lens. That instrument cannot do what the voltaic pile has done—effect decompositions which had never been effected before. To reduce the disturbing effect of heat as far as pos- sible, and give every advantage to the condensed lumi- nous focus, I received the cone of rays coming from the twelve-inch burning-lens on a glass globe (Fig. 96) six inches in diameter, filled with water. This increased the converging of the rays, and brought them more quickly to a focus. Then through the neck of the globe was introduced to the focus, in a matrass, spoon, or other