tidal or nontidal currents. At any rate, it was observed that although 
shoaling waves made angles with the shore line that should have resulted 
in a southward longshore current during 48 of 69 total observations, the 
direction of longshore flow was measured as northerly in 55 instances. 
The effect just mentioned seemed to be most readily exhibited when waves 
of low energy, with fronts nearly parallel to the shore (Figure 6, 3 
August) were common. Longshore current velocities ranged from nearly 
zero to 0.3 m/sec (0.6 kn). Rip currents (Figure 6, 2 August, 1200 hours) 
were rarely observed. ‘ 
Diffusion Measurements. Studies of turbulent diffusion in estuarine 
and inshore waters have given recent impetus to the development of a 
Superior technique for tagging water masses and detecting the decrease in 
concentration of the tag through time. Independent research by scientists 
of the Japanese Governmental Agencies (1958) and the Chesapeake Bay In- 
stitute (Pritchard and Carpenter, 1960) led to the selection of rhodamine- 
B dye, an organic pigment, as a tagging agent, and to the development of 
fluorescence analysis as a detecting technique. The fluorescence spectrum 
of rhodamine-B has a maximum at 575 millimicrons and use of a Turner Model 
III fluorometer permits detection to 0.02 - 0.004 ppb. A review of the 
technique and its limitations has been presented by Pritchard and Carpenter 
(1960). Studies by the Virginia Institute of Marine Science have utilized 
their experimental techniques. 
Okubo (1962) has made a comprehensive analysis of the recent theoret- 
ical treatments of diffusion in the sea and of the results of experimental 
studies. He proposes a solution to the diffusion equations (1962, p. 56) 
that involves an "energy dissipation" parameter having the dimensions 
cm2/3/sec. 
On August 1, 1962, between 0800 and 1400 hours, personnel of the 
Virginia Institute of Marine Science and the U. S. Coast and Geodetic 
Survey initiated, maintained, and monitored a continuous release of dye 
from a point approximately 800 meters off Cape Henry (Figure 7). The rate 
of release of rhodamine-B was 0.7 g/sec and the vehicle solution was 
adjusted to the density and temperature of the surrounding water (1.01 g/cc 
and 25°C, respectively). Release was from a point source at approximately 
4 meters depth. In addition, a small number of surface and bottom drifters 
were introduced at the point of dye release (Figure 7) to gain a crude 
measure of neighbor diffusion, in the event that the dye study should fail 
in some respect. 
Tide tables had indicated that slack water before flood would occur 
at 0800 hours on 1 August 1962. Thus, it was expected that the dye would 
be carried into the bay on the flood current. The flood current did not 
develop, however, and an ebb outflow began about 0900 hours. This led to 
an unusually long southward flow. (This flow was induced by an unusually 
heavy rainfall in the vicinity of Chesapeake Bay entrance on the previous 
day.) 
