USE OF OCEANOGRAPHY—DEACON 367 
the main features of the wave pattern can be predicted from the speed, 
direction, and duration of the wind in the locality and in the adjoin- 
ing ocean areas which contribute swell. These predictions are, how- 
ever, of an empirical nature and have mainly local validity; much 
more work must be done before they can be of general validity and 
universal application. Such work would undoubtedly prove useful 
in the design of ships’ hulls and in laying down operating speeds to 
suit different wave conditions, as well as in providing essential data 
for harbor design, coastal engineering, loading and unloading in 
exposed anchorages, passage over harbor bars, salvage operations, 
and oil drilling. 
We already have excellent charts of the prevailing ocean currents, 
but these charts are careful to point out that day-to-day speeds and 
directions are variable, even in regions of strong current. The first 
observations in the Gulf Stream, made more than a hundred years 
ago, showed that the current was unsteady, and that it shifted its 
position so that the set varied in strength and direction, especially at 
the edges of the current. Since then, the averaging of many thou- 
sands of observations has tended to encourage geographers to repre- 
sent the stream as broader and weaker than it really is. New 
observations between Cape Hatteras and Cape Cod, made with the 
help of modern radionavigational aids, show that the set in the fastest 
part of the current is often greater than is usually supposed; it reaches 
as much as 4 to 5 knots in a narrow region 10 to 15 miles wide near 
the landward side of the current. The observations show eddies 
varying from a few miles across to several hundred miles, and they 
also show that on occasion there can be strong countercurrents even 
near the usual axis of the current. Experiments by tanker companies 
operating along the U.S. Atlantic seaboard have shown that seeking 
out the strongest part of the current can save time. In regions of 
variable current a better understanding of the physical processes 
involved might improve safety measures. 
Although the techniques of recording, analyzing, and predicting 
tides and tidal streams are already very effective, long series of ob- 
servations cannot be made at every place for which predictions are 
required. To make the best use of a short or remote series of obser- 
vations calls for a clear understanding of the effect of the tide-raising 
forces on seas of different size and shape, and of the factors which 
modify a tidal wave entering shallow water. 
COASTAL AND HARBOR ENGINEERING 
There are many potentially useful applications of tidal studies in 
connection with the changes in estuaries and channels brought about by 
silting and erosion. In fact, the interests of hydraulic engineers and 
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