During the investigations of the geological structure of Barbados (British West Indies) in collaboration with the late A. J. Jukes-Browne and the late G. F. Franks, in the years 1884 to 1893, the results of which have appeared in a series of papers published in this Journal, a fairly complete examination of the coral-rocks of that island was made. An earlier very accurate examination was made by Sir Robert Schomburgk, and a good account of it was given in his ‘History of Barbados’ (1848). Schomburgk, as later we were, was struck with the occurrence of numerous beds of volcanic ashes characterizing the Oceanic Series of foraminiferal, radiolarian, and argillaceous deep-sea deposits so well exposed in Barbados. In the series of Globigerina Marls and Amphistegina Limestones and Basal Reef-Rocks, described on pp. 212 to 217 of the 1892 paper and on pp. 540 to 549 of the 1898 paper, fairly abundant proofs of volcanic activity in the Caribbean region during their deposition occur in the form of fragments of volcanic glass, felspar, and occasionally, though rarely, of pyroxene. But no ohserver found any beds of volcanic ash, or even any indication of volcanic activity, in the strata forming the coral-limestone terraces, the deposition of which probably began in the Pliocene, and certainly continued to recent geological times. In the 1891 paper I regarded the acid-insoluble residue of the coral-rock, the analyses of which are given in that paper, as consisting only of silica with clay, iron peroxide, and alumina, these constituents