Radioactivity of Sea- Water. 391 
j. Taken Nov. 8th ; lat. 44° 03' N., long. 10° 2V W. 
(About 80 miles north-west of nearest land, at entry of 
Bay of Biscay.) 
Radium 0*0146 x 10~ 12 gram per c.c. (no acid used). 
The mean of these results is 0*0172 x 10~ 12 and the mean 
of the maximum results on the five sea-waters is 0*0217 x 10 — 12 . 
More recently still a sample of sea-water reached me from 
the Arabian Sea. This was collected by my former pupil 
Mr. R. Friel, of* the Indian Civil Service. The bottle used 
was supplied by me. I concentrated this sea-water imme- 
diately on its receipt from its original bulk of 1550 c.cs. to 
1000 c.cs., acidifying it with 50 c.cs. of re-distilled HOI, part 
of which was used in washing out the bottle in which the 
sea-water travelled. The entire operation was effected in 
the Botanical Laboratory. The result was : — 
k. Sea-water from Arabian Sea, taken Nov. 25th, 1907 ; 
lat. 10° 40' N., long. 58° 0' E. (About 400 miles 
west of Cape Guardafui and 500 miles south of the 
coast of Arabia) : — 
Radium per c.c. 00243 x 10 — 12 first experiment. 
0*0314 „ second „ 
0*0278 „ mean result. 
Selecting the result c from the first experiments as derived 
from a true oceanic water, and accepting the general mean 
of the five samples of water taken between Madeira and the 
Bay of Biscay, and finally the mean result on the water from 
the Arabian Sea, we get a general mean of 0*0255 X 10 — 12 . 
Although it is my intention to add to these determinations, and 
more especially to examine water brought up from ocean depths, 
it seems allowable to conclude that results so sustained on 
waters derived from points so far separated, must represent 
approximately the radium content of oceanic water. Any 
other assumption seems inconsistent with the fairly uniform 
composition of sea-water, as regards other constituents, over 
the world, where special conditions do not intervene to 
dilute or concentrate it. Eve's result points, indeed, to 
possible deficiency of radioactive matter in central ocean. 
My own to some increase near the land. These indications 
call for further investigation. 
As to the validity of the determinations the general agree- 
ment among results arrived at, some by concentration, some 
by direct bottling of the water as it arrived, and again 
between samples evaporated in the Geological Laboratory 
and those evaporated in a building only just opened, leaves, 
