A recent visit to Central Germany afforded the writer an opportunity of studying the conditions under which the Vogelsberg iron-ore and bauxite have been formed, and a brief account of what was observed may assist in broadening the basis upon which a sufficiently comprehensive view of the origin of those substances may ultimately stand. On this account my visit to the region was approved by the Department of Agriculture in Ireland, in connection with the work now in progress on the iron-ore and bauxites of co. Antrim. In my traverses I enjoyed the very agreeable companionship of Dr. Schottler, of the Grossherzoglich Hessischen Geologischen Landestaldt, and the advantage of his guidance. His elaborate description of the basalts in the vicinity of Giessen has since been issued, and is referred to in this paper. The admirable and exhaustive accounts of the bauxite by Professor Adolf Liebrich, and of the iron-ore by H. Münster, are also appealed to frequently. Among other important papers consulted regarding the chemical processes involved may be mentioned those of M. H. Coquand, Professor G. A. Cole, F.G.S., M.E.I.A., Max Bauer, Sir T. H. Holland, A.R.C.S., F.E.S., H. Warth, D.Sc., & F.J. Warth, B.Sc., Malcolm Maclaren, B.Sc, F.G.S., H. Brantwood Muff, B.A., and the summaries by F. Wigglesworth Clarke and Dr. C. Doelter.