USE OF OCEANOGRAPHY—DEACON 369 
mouths and pierheads, which may add considerably to the difficulty 
of handling ships entering or leaving a harbor. Although the number 
of major ports seriously affected by this range action, as it is called, 
is small, there are some ports, such as Cape Town and Madras, where 
it is a serious problem. The recent International Navigational Con- 
gress (1957) urged that research be undertaken to establish the causes 
of the phenomenon, to predict disturbances likely to cause danger to 
shipping, to study the results of long-period waves, and to devise 
alleviating and remedial measures. Some evidence of increased silting 
due to this kind of oscillation was put forward at the congress. 
There are other kinds of oscillation which may contribute to the 
range action; long-wave energy may be transmitted from distant 
storms, and natural oscillations are also present in gulfs, bays, chan- 
nels, and larger areas of water such as the continental shelves. In 
small bodies of water shut off from the large oceans these oscillations 
are often more prominent than the tides; round the ocean coasts them- 
selves their effect can be seen on tide-gage records, which every now 
and then take on a saw-tooth appearance as the regular rise and fall of 
the tide is disturbed by the local oscillations. We know very little 
about the causes of these oscillations, but it is presumed that local 
meteorological conditions have much to do with them. Experience 
shows that, in the case of long waves started by submarine earthquakes, 
the energy contained in a short burst of long waves coming from the 
deep ocean can be trapped in slower waves running along a continental 
margin, so that oscillations in a coastal region may persist for several 
days. ‘There is also a possibility that disturbances may be prolonged 
by multiple reflections and refractions at the ocean boundaries, islands, 
and shoals. 
It is not known whether long waves can be generated in deep water, 
but in shallow water (50 fathoms) it is not unusual for a long wave to 
travel at the same speed as a meteorological disturbance (60 knots), 
and in such conditions the wave, once started, is continually energized. 
This happens every now and then in the English Channel; a small 
change in wind or atmospheric pressure traveling at just the right 
speed causes a long wave, and an observer on the beach can see the 
water ebb and flow several feet in as many minutes. Coming quite 
unexpectedly, it can cause considerable confusion among small craft 
near the beach and some trouble to people on the beach. 
The giant surges in the path of a hurricane, and when water is piled 
against a coast by a strong wind, are of much longer duration; they 
no longer appear as irregularities on a tide curve, but are as large as 
the tides themselves. Coasts near the path of typhoons and hurricanes 
and those with a wide, shallow shelf extending toward oncoming 
storms are the most vulnerable to flooding. They are the subject of 
