66 
curve a traverse is made across the area defined by their markers. 
From 2 to 10 samples are taken on these traverses which in some 
instances extend over several thousand feet. The maximum count 
obtained on the traverse is interpreted as marking the "center" 
of the sewage field and decreasing counts are interpreted as 
meaning departure to varying degrees from the main field. The 
line shown in Figure 17 is an approximate "best fit" drawn through 
the medians of their disappearance values at the various times of 
sampling and is interpreted as representing the average picture. 
Apart from the differences in the nature of the experiments, 
there are no apparent differences in the techniques employed for 
determining coliforms that would account for the differences in 
results. Dr. Mittwer has observed the LASD techniques and Mr. 
Garber has observed those of the Hancock Foundation. Both are 
satisfied that the techngiues are essentially similar. Personnel 
of the AHF have usually employed five tubes per dilution in the 
dye patch experiments whereas the LASD have employed two tubes. 
Although this might make our individual determinations a little 
more accurate, it should not affect the general findings. We 
have always taken our samples from the dyed area while many of 
theirs were taken from areas there no dye was present. The 
possibility that the dye used might be toxic to coliforms was 
considered, but laboratory experiments failed to show any toxicity 
whatsoever at concentrations much higher than those present in 
the dye patch. 
The grids run at Whites Point and at Hyperion show that large 
variations in coliform counts are observed in samples taken almost 
simultaneously over a small area of ocean surface. It was pointed 
