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XXII. 
THE RADIOACTIVITY OF SHA-WATER. 
By J. JOWY, Sc.D.) ERS:, 
Professor of Geology and Mineralogy in the University of Dublin. 
Hon. Sec., Royal Dublin Society. 
[Read, Novempsr 19; Received for Publication, NovEMBER 22, 1907 ; 
Published, January 15, 1908.] 
I am acquainted with only one determination of the radium in 
sea-water taken directly from the ocean—that recorded by 
A. 8. Eve in his paper “ On the Ionization of the Atmosphere over 
the Ocean.” Strutt had previously determined the radium in 
sea-salt,? and obtained the value 0°15 x 10-” in grams per gram 
of salt. This must be reduced, however, to about one-half, seeing 
that, at the time of this determination, the quantity of radium 
associated with a gram of uranium was believed to be about 
double as great as it has since been shown to be—this quantity 
entering into the calibration of the electroscope. It is necessary 
to add that Strutt gives his determination as ‘“ approximate 
only.” 
The sea-water dealt with by Eve was collected in mid-Atlantic, 
between Montreal and Glasgow. The amount of radium found 
was 0:0003 x 10“ grams per gram of sea-water. If we reckon 
sea-salts as composing 3 per cent. by weight of sea-water, Strutt’s 
determination would give 0:0023 x 10 grams per gram of 
sea-water. 
Eve also made an experiment on sea-salt, using 400 grams of 
Omaha sea-salt guaranteed pure by the importers. He finds 
0:02 x 10°” grams per gram, or for the equivalent sea-water, 
0:0006 x 107”. 
We thus have the three divergent results :— 
From radium in sea-salt (Strutt), 0°:C023 x 10-”. 
From radium in sea-salt (Eve), 0-0006 x 10-”. 
From mid-Atlantic sea-water (Eve), 0-0003 x 10. 
1 Phil. Mag., vol. xiii., Ser. vi., p. 248. 2 Proc. R. 8., vol. Ixxviii., p. 161. 
SCIEN. PROC. R.D.S., VOL. XI., NO. XXII. 2 
