IN order to find experimental support for the theory of X-ray diffraction in liquids put forward some three years ago by C. V. Raman and K. R. Ramanathan (Proc. Indian Association for the Cultivation of Science, vol. 8, p. 127, 1923), extensive studies have been undertaken in the authors' laboratory of the phenomena observed when a pencil of monochromatic X-rays passes through a layer of fluid, particularly with the view of determining how the effects are influenced by the physical condition and the chemical nature of the substance under investigation. The photographs here reproduced (Fig. 1, a and b) were obtained in the course of work on this line by one of us (C. M. Sogani) and represent the X-ray liquid haloes of hexane and cyclo-hexane respectively. The fluids were contained in cells with very thin walls of mica, and the K-radiation of copper from a Shearer X-ray tube was used.