Diffusion was investigated in one of the tidal currents 
during ebb flow by continuous tagging with rhodamine-B dye 
at the rate of 0.7 g/sec and by monitoring dye concentrations 
with fluorimeters. A log-log plot of a "concentration ratio,” 
c-M-!-D vs x, for values of x between 800 and 3800 m, fitted 
an x-l relationship where c equals peak dye concentration, M 
equals rate of dye discharge (g/sec), D equals layer depth (m) 
and x equals distance along the axis of the plume. Neighbor 
diffusivity, F (2) had a minimum value of 316 cm2/sec and the 
coefficient e€ , in F (£) = 67/3 had the minimum value of 0.062. 
INTRODUCTION 
Circulation along the ocean flanks of the mouths of. large estuaries 
has been studied little. Our attempts to understand the circulation in 
the vicinity of the southern flank of the entrance to Chesapeake Bay 
(Figure 1) have been prompted by the practical considerations involved 
with locating submarine sewage outfall pipes and the recommendation of 
beach protection measures along the shore line of Virginia Beach, Virginia 
(Figure 1). The sum of previous work in the area known to us consists of 
current observations from lightships by Haight (1942, Figure 15), of 
measurements of the U. S. Coast and Geodetic Survey summarized in Special 
Publication 162, of drift bottle surveys mentioned by Joseph et al. (1960) 
and Norcross et al. (1962), and of casual observations reported in a beach 
erosion study by the U. S. Army Corps of Engineers (U. S. Congress, 1953, 
p. 15). In combination, these sources suggest that the offshore shelf 
waters exhibit a dominantly southerly drift, but that the inshore waters 
south of Cape Henry, to an unknown distance seaward of the shore, describe 
a clockwise eddy movement extending “approximately 3 to 4 miles south of 
Cape Henry" (U. S. Congress, 1953, p. 15). Our examination of the grosser 
aspects of the circulation began with the drift bottle releases described 
below. 
RESULTS OF DRIFT BOTTLE RELEASES 
A total of 898 drift bottles were released at the five stations 
shown on Figure 2, during the months of April, May, June, July, August, 
and October 1962. Results of the releases are summarized in Table 1 
and Figure 2. 
