PLATE 5 
Fig. 5. Chart showing bottom conditions at 64 stations in San Francisco 
Bay, based upon the analysis of samples taken in part with the dredge, in part 
with the bottom-sampling apparatus. Of the latter, the superficial layers only 
are included in this chart. 
In these symbols, percentages by weight of the various sized particles have 
been indicated by the relative areas of the sectors. The finest dots denote 
sand (i.e., particles less than two millimeters in diameter, but coarser than 
mud); the next larger ones represent particles 2 to 5 millimeters in diameter; 
the next 5 to 10; and the largest ones particles over 10 millimeters in diameter. 
Mud is represented by the uniformly black areas. Calcium carbonate is repre- 
sented by the white circles at the center of certain of the symbols. The area 
(not the diameter) of this inner circle is proportionate to the percentage of 
calcium carbonate in the sample. (See pp. 95, 96 for fuller explanation.) 
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