Absorption-bands in Colourless Liquids

IN the obituary notice of the late Dr. W. J. Russell, F.R.S. (NATURE, November 25, p. 101), whose genial friendship I enjoyed and with whom, when occasionally in London, I had friendly intercourse, it is stated that he had published “papers conjointly with Mr. Lapraik on absorption spectra, and notably one on the absorption bands in the visible spectra of colourless liquids, which was the pioneer paper in a branch of inquiry that has been ably followed up by Prof. Noel Hartley, F.R.S., Mr. E. C. C. Baly, F.R.S., and. others.” It seems ungracious to call in question the accuracy of this reference, and I feel, indeed, a great inclination to let it pass without comment, although it is incompatible with authoritative statements made elsewhere; but, inasmuch as the passage is liable to be reprinted without question and repeated in other publications, I consider it would be better to invite the writer's attention to the Chemical Society's Transactions, xxxix., 153–68, 1881, “Researches on the Relation between the Molecular Structure of Carbon Compounds and their Absorption Spectra”, and suggest that he should compare it with the paper which follows in the same volume, pp. 168–73, “On the Absorption-bands in the Visible Spectrum produced by Certain Colourless Liquids”. Having done so, I think he will agree that not only is the latter not the pioneer paper, but also that there is very little in common between the two. In fact, the latter communication is more closely allied to the work of Abney and Festing in the infra-red region, a work to which the authors themselves make a special reference.