386 Prof. J. Joly on the 
0*1.5 x 10" 12 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 -12 gram per gram of sea-water. 
If w r e reckon sea-salts as composing 3 per cent, by weight of 
sea-water, Strutt'* s determination would give 0*0023 x 10 -12 
gram 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~ 12 gram per gram, or for the equivalent sea- 
water, 0*0006 x 10- 12 . 
We thus have the three divergent results : — 
From radium in sea-salt (Strutt), 0*0023 X 10~ 12 . 
From radium in sea-salt (Eve), 0*0006 x 10~ 12 . 
From mid-Atlantic sea-water (Eve), 0*0003 x 10 " 12 . 
In reviewing these figures Eve states that it is safe to con- 
clude that sea-water does not contain more than 0*0006 x 10~~ 12 
gram radium per gram. 
In April of the present year a friend sent me from 
Valencia, Co. Kerry, a sample of sea-water collected in the 
harbour at flood-tide. A very large volume of water enters 
this extensive harbour at each flood ; and as there are no 
large rivers along the coast, water taken at the harbour mouth 
may be regarded as free from impurities derived from the 
shore. The quantity sent to me (in a stoppered glass bottle 
which I had transmitted, specially cleansed, for the purpose) 
was 2450 c.cs. This was evaporated on the water-bath to 
about 1200 c.cs., with every precaution against contamination, 
and in a part of the laboratory in which radioactive prepara- 
tions had never come. The radium determined in this 
Valencia sea-water was 0*0356 x 10 -12 gram per gram. The 
apparatus and mode of extraction I was using at this time 
were closely similar to those developed by Strutt as described 
in his paper (loc. cit.). The readings of the electroscope 
were standardized by the emanation from Joachimsthal 
pitchblende, a portion of which I had analysed for the 
uranium. 
This determination, showing more than ten times the 
