THE annual report, written by Mr. Cyril Bergtheil, of the Indigo Research Station of the Bihar Planters' Association for the year 1907–8 has just been issued; it contains an interesting statement with regard to the value of “synthetic” indigo as a dye-stuff compared with natural indigo. From last year's experiments (see NATURE, vol. Ixxv., p. 614) it was concluded that “synthetic” indigo gives poorer results under practical conditions than those obtained with the natural dye, the latter imparting a richness of shade or “bloom” which was unobtainable with the synthetic material. It has since been ascertained that the synthetic indigo supplied for the tests was “brand E” of the Badische Anilin- und Soda Fabrik, which contains some 25 per cent, of lime; the presence of this high proportion of alkali would of itself account for the bad results obtained in the hydrosulphite vat. Experiments will now be made using the material which the Badische company itself recommends for the hydrosulphite vat.