Points from Foregoing Letters

Abstract

THE radium content of sea water is found by E. Föyn, B. Karlik, Prof. H. Pettersson and E. Bona to vary between 0.03 and 0.2 × 10^-2 gm. per litre. Even the larger figure corresponds to only about one fifth the amount to be expected from the uranium present in sea water (2 × 10^-6 gm. per litre), and the authors consider that the larger part of the radium (or rather its parent ionium) is precipitated together with iron in clays and other marine deposits. The same occurs to a lesser extent with thorium, of which only half the expected amount is found in the sea water.