-
level,
21
-
of 1,300 disintegrations per minute, was almost
as high as the maximum level recorded by the Taney
survey of 1955,
so that
it was assumed that the entire
area covered by the Walton was contaminated to some
extent.
The
levels of plankton contamination,
highest
north of Bikini, diminished rapidly to the south and
trailed off gradually to the northwest,
except that
there was a long stream of plankton contamination
extending from Eniwetok to Bikini and on to the southwest
corner of the survey area,
for more than 300 miles.
a stream identifiable
Examination of the measure-
ments by the probe showed that the curves checked
closely with those produced by the surface water
samplings on most of the fifty-three stations.
After completion of the 1956 test series the second
oceanographic cruise ship,
zigzag passages,
the U.S.S. Marsh
(DE 699)
made two
one east to west and one west to east from
Eniwetok Atoll to Guam and return.
The cruise lasted twenty
days during which samples of sea water and plankton were collected at seventy-four stations.
The spread of the contaminated
water during the six-week interval between the Walton and Marsh
surveys and the decrease in radiation as determined by the water
and plankton samples may be summarized as follows:
The Marsh brought back the answer to the question
of how far and at what levels of activity contamination
had moved westward.
At Guam,
samples of water showed
very low levels of radioactivity,
yet the values at the