The radium content of twenty-eight (twenty-seven from the Pacific) samples of ocean-bottom sediments was determined, and similar determinations reported by Joly and Pettersson are included for comparison. These comprise practically all such determinations that have been made, and the paucity of these data in comparison to the extent, importance, and high radium content of the material is emphasized. Those bottoms composed mostly or entirely of red clay generally contain more radium. A mechanism for explaining the high radium content of deep-sea sediments is suggested which does not coincide with the opinions of either Joly or Pettersson.

From 1983 until 1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions. At the time it was the most extended data compilation on ferromanganese deposits world wide. Initially published in a proprietary format incompatible with present day standards it was jointly decided by AWI and NOAA to transcribe this legacy data into PANGAEA. This transfer is augmented by a careful checking of the original sources when available and the encoding of ancillary information (sample description, method of analysis...) not present in the NOAA-MMS database.

Supplement to: Piggot, C S (1933): Radium content of ocean-bottom sediments. American Journal of Science, s5-25(147), 229-238