I HAVE been greatly interested in your note on M. Renard's researches as to the composition of the volcanic material ejected during the recent eruption of Krakatoa. The ashes, as stated, are those of a magma that would have produced an andesite with rhombic pyroxene. Now such an andesite occurs at so many points, and in such immense masses, round the great Pacific “circle of fire,” that one is tempted to ask if it may not specially characterise this important volcanic region. I will, with your permission, briefly refer to some published, and one or two unpublished, facts with regard to the distribution of this andesite (called hypersthene-andesite by Whitman Cross and Iddings, and bronzite-andesite by F. Becke) round the Pacific circle.