I have read with very great interest Dr. Peacock's paper on the distinction between palagonite and chlorophaeite in the Geological Magazine, for April, 1930. On p. 170 thereof, Dr. Peacock gives a brief summary of my conclusions upon the nomenclature of chlorophaeite and palagonite as given in my paper on the same subject. Briefly, my conclusions are that as far as can be judged from existing analyses, the hydrous glassy material forming a portion of the rocks originally called palagonite has a composition that brings it within the range of composition exhibited by various specimens of chlorophaeite, and that, therefore, the term palagonite should be reserved for the impure rock, and the term chlorophaeite used for this hydrous glassy material. It was also recommended by me that the process by which in the case of the basaltic tuffs the primary glass becomes hydrated should be termed palagonitization and that the same term should be applied to the process by which the interstitial glass of basaltic lava flows is altered with production of chlorophaeite. The fact that olivine, if present, a portion of the augite, and occasionally some of the felspar, may also suffer similar alteration or be replaced, is not regarded by me as pointing to an essential difference in the two processes.