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Published online by Cambridge University Press: 17 January 2013
At the end of 1886 a method occurred to me of rapidly recording the positions of the lines of the solar spectrum, which I thought might be used with advantage for determining the faint “Telluric dry-gas lines” near D, mentioned in Professor Piazzi Smyth's maps of The Visual Solar Spectrum in 1884. The fundamental idea of the recording apparatus is that of magnifying by some mechanical means the motion of the grating, or prism, to such an extent that it can be recorded on a continuous fillet of paper. The viewing telescope being then firmly clamped, the exact positions of the grating can be pricked off on the strip of paper as the lines are successively brought to the fixed cross in the field of view.
For the satisfactory use of the method two conditions suggest themselves as desirable. First, the punctures should not be less than a good-sized pin hole, and the interval between the closest lines, which the spectroscope is able to separate, should be represented on the paper strip by a space of several tenths of an inch.
page 99 note * Trans. Roy. Soc. Edin., vol. xxxii. part 3.
page 101 note * Upsal, 1868.
page 101 note † Trans. Roy. Soc. Edin., vol. xxxii. part 3.
page 112 note * Compare Hasselberg, , Untersuchungen über das Absorptionsspectrum des Jodgases. St Petersburg, 1889Google Scholar.
page 115 note * American Journal of Science, vol. xxxiii., March 1887Google Scholar.
page 115 note † Publicationen des Astrophysikalischen Observatoriums zu Potsdam, Fünfter Band, Potsdam, 1886Google Scholar.
page 118 note * Vierteljahrsschrift der Astronomischen Gesellschaft, 25 Jahrgang, Erstes Heft, Leipzig, 1890Google Scholar.
page 118 note † Bessel, , Fundamenta astronomiæ …. Regiomonti, 1818Google Scholar, Sectio iv.
page 119 note * Laplace, , Traité de mécanique celeste, Tome iv. livre x. p. 246. Paris, 1805Google Scholar.
page 121 note * Laplace, ibid., No. 5.
page 121 note † Laplace, , Traité de mécanique céleste, Tome ivGoogle Scholar. livre x. chapitre iv.
page 131 note 1 Phil. Trans., vol. 150, 1860, p. 154, London, 1861Google Scholar.
page 131 note 2 Phil. Mag., August 1845, p. 85Google Scholar.
page 132 note 1 Recherches sur le spectre solaire, p. 40.
page 132 note 2 Vierteljahrsschrift der astronomischen Gesellschaft, 25 Jahrg., 1 Heft. Leipzig, 1890Google Scholar.
page 134 note 1 M. Thollon's maps, which we have just received (see Postscript), give water-vapour lines in the α-group, the middle of the band being in 
= 1586. Each of the first three bands of the series is thus followed by a group of lines which are fainter than the bands themselves.
page 134 note 2 The Catalogue begins on p. 48.
page 135 note 1 The maps have been reproduced by photo-lithography, and are about one-fourth of the size of the original drawings. It will be noticed that the faintest lines are far from continuous in the lithographs, but as it was found impracticable to make good this defect without altering the breadth of the lines, they are left untouched.
page 135 note 2 Paris, 1890.
page 137 note 1 On p. A15, loc. cit., there is a table of water-vapour lines in which the figures do not agree with those given above. M. Thollon gives 107 telluric lines more than we counted from the book. We reproduce his summary:—
