3.  Sediment-Size Distribution. 
The median grain size (by the dry sieve method) of the sand at the 
beginning of the 1971 experiments (Vol. III) was 0.23 millimeter. The 
median grain size (by the dry sieve method) at the beginning of the 
experiments conducted immediately preceding the experiments in this 
study in each facility (Vol. VI) was 0.22 millimeter. Samples were 
not collected before the start of experiments 72B-06 and 72B-10, but 
the 0.22-millimeter value is assumed to still be an accurate estimate 
of the initial median grain size. 
All samples collected for the experiments were analyzed by the Visual 
Accumulation (VA) tube method and 10 percent of the samples were also 
analyzed by the dry sieve method for quality control (described in Vol. 
I). The median grain-size results determined by the dry sieve method 
(Table A-2 of the App.) are generally 0.015 millimeter greater than the 
VA tube. The VA tube values are used here only because all samples were 
reduced by this method. The initial median grain size (by the VA tube 
method), for comparison with these results, is assumed to be 0.205 
millimeter. 
Table 9 gives the median grain-size data at 50, 100, and 150 hours in 
experiment 72B-06; Table 10 summarizes the results by profile zone (data 
are unmodified VA tube results). In the foreshore zone, the mean of the 
medians increased as the experiment continued, but the range of medians 
decreased. In the inshore zone the medians increased at 50 and 100 hours, 
then decreased at 150 hours, and the range of values remained quite small. 
The mean median size in the offshore zone decreased at 50 hours, then in- 
creased to the initial value at 100 and 150 hours; the range of values 
varied from 0.02 to 0.05 to 0.04 millimeter. The average median of all 
samples collected was 0.206 millimeter, close to the assumed initial 
median. 
Table 11 gives the median grain-size data at 50, 105, and 150 hours 
in experiment 72B-10; Table 12 summarizes the results by profile zone. 
In the foreshore zone the mean median size increased 0.02 millimeter at 
50 and 105 hours and then decreased 0.01 millimeter at 150 hours, while 
the range of values decreased from 0.08 to 0.07 to 0.06 millimeter. In 
the inshore zone, the mean median increased 0.01 millimeter at 50 and 105 
hours and then remained at 0.22 millimeter at 150 hours, while the limits 
of the values fluctuated somewhat. The’ mean median size in the offshore 
zone decreased 0.02 millimeter at 50 hours, increased 0.01 millimeter 
at 105 hours, and remained constant at 150 hours; the range increased 
slightly, then increased greatly, and finally decreased greatly. The 
average median of all samples collected was 0.200 millimeter, fairly 
close to the assumed initial median. 
The results of both experiments are typical of eroding profiles. 
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