ship would have had the same effect and could 
only have been overcome with some kind of sea 
anchor. 
Despite the scatter due to these fluctu- 
ations, the points in Figure IV show a distinct 
over-all trend, especially after the obser- 
vation nearest the surface has been corrected 
for the ship's bottom signal by reference to 
the curve in Figure III. If the profile is 
taken to be a straight line with a slope of 
about 1.5 millivolts per 100 meters, one ob- 
tains a uniform flow velocity relative to the 
ship of about 1.5 knots to eastward. There is 
some suggestion of a steeper voltage gradient 
at the lower depths, corresponding to an east- 
ward flow of 2 knots or more. These velocities 
will be somewhat low because meter wheel readings 
were used instead of the true depths. 
It should be emphasized that it is only 
the east-west component of the flow velocity 
relative to the ship which is determined 
directly by vertical measurements of this sort. 
To obtain the true east-west flow velocity, 
one must add the eastward set of the ship as 
determined by loran, by horizontal G.E.K. 
measurements, or by carrying the vertical 
measurements to still water at great depths, as 
suggested by Malkus and Stern. 
At this station, the loran determinations 
gave a set eastward of 1.7 knots corresponding 
to a true eastward flow velocity of about 3.2 
knots. Horizontal G.E.K. measurements made in 
the same vicinity several hours after the 
vertical measurements, indicated a set to east- 
ward of 1.4 knots. 
The vertically measured 1.5 knot flow 
velocity relative to the ship is due, of course, 
to the wind drift of the ship. Had there been 
no wind, so that the ship coasted with the Gulf 
Stream, no vertical potential gradient would 
have been observed on this shallow lowering. 
Approximately this situation arose the follow- 
ing day when the next lowering was attempted 
in the same general area. The estimated loran 
set was about 3.2 knots to eastward; the verti- 
cal voltage gradient, if any, was less than 
0.1 millivolt per 100 meters. 
Because the results of these three 
lowerings were grossly misinterpreted at the 
time, due to the adverse effect of the sea 
state on the Chief Scientist, the vertical 
measurements were prematurely discontinued. 
No really deep soundings were attempted. It 
now appears that deep soundings could be 
carried out using the same procedures without 
difficulty. 
TOWING TESTS 
For towing experiments of the type 
182 
customarily made with the G.E.K., we used a 
pair of lines taped together, one 200 meters 
long, the other 100 meters long. This gave a 
100 meter probe interval towed at 100 meters 
behind the ship. 
Though the polyethylene tubing is nowhere 
near as strong as the conventional G.E.K. line, 
it bore up quite well under sustained towing at 
10 knots. But it could not, we discovered, take 
the sudden strain of being brought up short 
after 100 meters or so had been let out all at 
once. This treatment snapped 100 meters off the 
long line of the towing pair during the first 
tests. As the failure occurred at a welded 
joint, it is possible that a single continuous 
line would not have failed. 
We had some difficulty in repairing this 
tubing successfully, since the repair weld was 
made perforce with tubing which had been exposed 
to sea water, These joints gave way or sprang 
leaks with great rapidity. We finally got a 
weld to hold together permanently by taping the 
line into a loop, so that the strain by-passed 
the joint. 
With this repaired line, we were able to 
make a continuous G.E.K. record from the Conti- 
nental Shelf to Woods Hole harbor. The record 
was satisfactory in every respect. 
Figure V is an excerpt from that record 
showing the signals obtained on running a square. 
The pattern shows the expected symmetry around 
the electrode zero. 
SEA WATER THERMOCOUPLE 
The sea water salt bridge is theoretically 
free of first order errors due to variations in 
pressure, temperature, or salinity. These are 
all supposed to be the same in both electrode 
chambers regardless of what may be happening in 
the sea. There is, however, a possibility of 
second order errors if the changes in one 
variable in going around the circuit do not 
coincide with the changes in another variable. 
If one constructs a sea water thermocouple 
with high salinity water as one element and low 
salinity water as the other, one can produce an 
EMF by heating one junction between the two 
while cooling the other junction. Part of this 
EMF will be due to the temperature coefficient 
of the liquid junction potential between the 
two; part will be due to a concentration de- 
pendence of the Thomson EMFs in the arms. 
We have constructed such sea water thermo- 
couples, and find that the EMF is about 0.2 
microvolts per degree per part-per-thousand 
salinity difference. 
