[PRELIMINARY NOTICE] HAVING occasion to examine the absorption spectra produced by considerable thicknesses of alcoholic solutions of certain cobalt salts, we were led accidentally to observe that alcohol alone gave a very distinct band, and afterwards, on examining water, found that it also, when a column of six feet was used, gave a very distinct absorption band in the orange, a little on the less refrangible side of D. By graphical interpolation we find the centre of this band to be about 600, and that the band extends from 607 to 596. This position corresponds very closely, if it be not identical, with Piazzi Smyth's rain-band,1 and also with the band seen in 330 feet of high-pressure steam by Janssen.2