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

  • John William Draper
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.

    443/488 (page 439)
    pressing on the ether during cooling a corresponding!}^ prolonged series of motions. And is not this the cause of that remarliable relation between the atomic weights of elementary bodies and their specific heats, discovered by Dulong and Petit ? These considerations may lead us to inquire whether the general cause of the decomposition of compound bod- ies by radiations is due to the circumstance that all the atoms of which their molecules are composed take on the vibratoiy motion with unequal facility. Thus if a cer- tain compound molecule be submitted to the influence of an intense radiation, some of its constituent particles may vibrate consentaneously at once, and others more tardily. Under these circumstances, the continued existence of the group may become impossible, and decomposition en- sue in the necessity of the case. In entering upon the experimental analysis of the ac- tion of a ray upon a decomposable body, there are three difterent points to be considered, so far as the ray itself is concerned: 1. To what extent and in what manner is the result affected by the intensity of the ray, or by the amplitude of the vibrating excursions ? 2. How is it af- fected by the freqvency of the pulsatory impressions? and, 3. How by the direction in which the vibrations are made, as involved in the idea of polarization? I shall now examine these in succession. 1. 2h what extent and in tvliat manner is the decompo- sitio7i of a compou7id body affected hy the intensity cf a ray or the am])litude of the vibrating excursions ? If the different degrees of facility wath which atoms receive the impression of ethereal vibi-ations be the true cause of decomposition by light, we should expect that many such changes would become possible under the in- fluence of a burning-lens which are not so in the direct rays of the sun.