1. 1891. ‘Scientific Transactions of the Royal Dublin Society’ Vol. iv, 571–571. Note by the Translator.—The presence of double lines in a series seems to indicate that the single motion in the gas which originates the whole series consists of partials, each of which is in general elliptic; becoming linear when the constituents of the double lines are of equal intensity, and circular when, as in lithium, one of them vanishes. That the double lines have equal intervals on a map of oscillation-frequencies seems to betoken that the path of that motion in the molecules of the gas to which the series is due is affected by an apsidal shift. See
2. 1890. The hydrogen lines inserted forcomparison with Series (b) are determinations by Ames ; Phil. Mag., July see