1914] Sumner, et al.: Physical Conditions in San Francisco Bay 101 
rivers is from ten to twenty times as great as in the fall, so that an 
appreciable dilution of the coastal waters might then be expected. 
17. The mean salinity of San Francisco Bay, so far as we may 
judge from the year covered by our observations, appears to be over 
twice as great as that of Chesapeake Bay, while it is considerably less 
than that of Buzzard’s Bay, on the New England coast. 
18. A physical analysis was made of bottom samples from seventy- 
nine stations, the proportions of ingredients of various grades of 
coarseness being determined. The percentage of calcium carbonate 
(derived nearly or quite exclusively from shells) was hkewise deter- 
mined for all of the samples taken, while the nitrogen content was 
ascertained for a selected series by the United States Bureau of 
Chemistry. : 
At twenty-seven of the stations, long cylindrical samples were 
taken with a special bottom-sampling apparatus devised for the pur- 
pose. These made possible a study of the natural stratification of the 
bottom. In the case of such samples, from two to four segments were 
analyzed separately. 
Few general statements can be made regarding the distribution, 
either horizontal or vertical, of the various types of bottom materials 
in San Francisco Bay, and the reader is therefore referred to the 
charts (plates 5, 6, 7), which depict these data. 
Transmitted January 13, 1914. 
