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.

    67/396 (page 43)
    former experiments, and therefore cannot be compared with those. No. Time. Portion olspectnim. Relative cliemical action. 1 II. M. 9 44 A..M. From % GH to I . . 14-5 9 48 .\.M. From N3 to R„ . . . 10-1 3 9 54 .V.M. From yV KoS to 4 ST . 2-4 4 9 59 A.M. From i ST to U . . 0 0 .5 10 4 A.M. From G to ^ GH . 13-0 6 10 8 A.M. From F to T FG . . 7-1 7 10 11 A.M. From 5 to 4 FG . . 3-2 8 10 15 A.M. From .4 DE to f EF . 0-4 From this it is seen that the relation of the chemical action of the spectrum from the line E to the line H undergoes a consider- able alteration Avhen the rays have to pass through a column of air 10,735 metres in height instead of 9,647 metres. An extended series of measurements of the chemical action of the several portions of the solar spectrum under various con- ditions of atmospheric extinction may prove of great interest, if, as we can now scarcely doubt, the solar spots appear at regular intervals, and our sun belongs to the class of fixed stars of variable illuminating power. It is possible that such obser- vations, made during the presence and during the absence of the solar spots, may give rise to some unlooked-for relations con- cerning the singular phenomena occurring on the sun’s surface. Whether, however, the atmospheric extinction can ever be determined with sufficient accuracy to render visible the alter- ation in the light which probably occurs Avith the spots, is a question which can only be decided by a series of experimental investigations which must extend far beyond the scope of any single observer.